Luck Manipulation Mechanic

Many games that involve an element of luck use dice rolls (or an equivalent, such as random number generators for video games, drawing cards in card games, and so on) as a means of determining the outcome of a certain attempted action. In many cases the total "success" of the attempt is determined by adding static modifiers to the number rolled, but the dice roll itself cannot be changed beyond that: A poor roll represents bad luck, whereas a high roll represents good luck.

Some games, however, incorporate mechanics that allow a player to alter their luck by re-attempting the die roll if they do not like the original result, usually in an effort to achieve something more satisfactory. By re-rolling the original die, the player can in this fashion pull victory from the jaws of defeat.

The exact nature of this mechanic, and the limitations on its use, vary from game to game. While some games may only allow the player a single re-roll of the die and force them to accept the new result, other games may include a means of rolling multiple dice at once and allowing the choice of the result that is most preferable for the player. Usually this works as limited Plot Armor. This type of mechanic can sometimes be used offensively, by allowing the player using it to force another player to re-roll their (formerly good) die result.

The Luck Manipulation Mechanic may be used as a means of representing the in-universe nature of a character that is Born Lucky, or one who has the power to invoke Winds of Destiny Change. When the mechanic is inverted (by forcing a player to choose the least preferable result), it can represent Born Unlucky instead.

Compare Luck Stat, which is a stat that passively provides bonuses or penalties to random game elements. Contrast Honest Rolls Character, where the player or Game Master limit themselves to only accepting their initial stat rolls at character creation, with no re-rolling or "dice fudging" allowed.

Please note that in order to qualify for this trope, the Luck Manipulation Mechanic must be deliberately designed into the game. Cheating methods that allow for similar results (such as Save Scumming, including the Tool Assisted Speedrun type and/or placating the Random Number God) don't count.

Board Games

 * Descent Journeys In The Dark has "Aim" and "Dodge" abilities that allow players to re-roll dice used in an attack (Aim) or force the player attacking them to re-roll (Dodge). Hero players can set either one as an order, the Overlord has cards that allow him to use these abilities.
 * Talisman:
 * Fate tokens, introduced in the revised fourth edition, allow the player possessing them to re-roll any single die at-will, expending the token in the process. Players are given a certain amount of fate tokens at the beginning of the game based on the character they are playing, and have means of gaining (or losing) more tokens throughout the game.
 * The Warrior character has this mechanic directly incorporated. During battle, the player controlling the Warrior rolls two dice instead of the standard one, and chooses the result they wish to keep.
 * The Misfortune spell allows a player to negatively affect another player's luck, by changing the result of any single die roll to a "1".
 * The Prophetess character allows the player controlling it to manipulate the "luck of the draw" by re-drawing cards from the adventure deck if they do not wish to keep their original draw. The Orb of Knowledge object offers a similar mechanic to characters who possess it.
 * Arkham Horror has "Clue Tokens" that represent various bits of Mythos-lore the characters have learned through their combing the city. Spending a clue token after a die roll lets you roll an additional die, and you can continue to roll as long as you have tokens to spend, some Skills even add 2 dice instead of 1 per token to certain kinds of rolls.
 * Yahtzee incorporates this as a core game mechanic. Players roll five dice each round, and if they don't like how they come up, they can re-roll some or all of them up to twice in one turn in attempts to get specific dice combinations.
 * Blood Bowl has "re-rolls", which each team gets a limited number of at the start of the game. They can be used at any time to re-roll one of the player's own dice rolls that the player doesn't like. Different teams get different numbers of re-rolls, representing differing levels of luck.
 * The "Advantage" token is used this way in Breakout: Normandy - after using it, however, one must pass the Advantage to the enemy, plus it's worth something in the endgame point count, meaning both players have an incentive to hold onto it until desperate times. However, an exceptionally bad result can cause either player to forfeit the Advantage involuntarily (the "bad result" ceiling is lower for the Allies to represent the extra political sway of heavy losses on the populace back home), giving both players an incentive to use it before they lose it as well.
 * When playing Race For The Galaxy, the "Exploration" phase is the only method by which you can gain new cards. During exploration, depending on how you play it, you draw three cards and keep two, or draw seven cards and keep one. Some of the improvements you play allow you to draw more cards as well, but you'll never get to keep more than two. If you're looking for a specific card, then you'll want to draw more (it also denies cards to other players, at least temporarily).

Card Games

 * Some card games, such as the original Star Wars Customizable Card Game and the Warhammer 40,000 Trading Card Game use numbers printed on the cards in place of die rolls, so a 'random' number is generated by revealing the top card of your deck. Naturally, this opens up plenty of combo opportunities with abilities that let you know (or even choose) what that next card will be.
 * The Munchkin card game has several cards and extra collectibles that allow manipulating the dice.
 * Magic: The Gathering:
 * Krark's Thumb and Goblin Bookie, allow you to re-flip a coin if you lose the flip.
 * The "Scry" ability on many cards in the 2011 Core Set, which allows you to look at the top few cards of your library (how many depends on the specific card), rearrange them, and sent the ones you don't need to the bottom of your library.
 * Fetch lands (lands which search your library for another land and put it in play tapped, but are sacrificed in the process) are often used for "deck-thinning". Many players even put these into mono-color decks, where any old basic land would work better, since fetch lands typically bring it into play tapped, and some require you pay life.
 * YuGiOh has Second Coin Toss, and a similar card for die rolls.
 * ...Which is called, oddly enough, Dice Re-Roll. However, its wording says that you HAVE to re-roll, regardless of outcome. It also has to be active before the roll in question is made.
 * Pokémon Trading Card Game: Sabrina's ESP from "Gym Heroes" lets you re-flip coins for attacks.
 * Victini from "Red Collection" has the same effect.
 * Draw poker incorporates this into its rules. Once per hand, you can Discard and Draw as many cards as you desire.

Tabletop RPGs

 * Generally, it's often used as extension of Plot Armor mechanics and quantified as number of points to avoid removing the risk completely. Since it should be limited, usually this means a Player Character has certain number of "bennies" that can be spent on a re-roll and may have other uses; they may or may not be "rechargeable" or persistent. There's a subset of mechanics that allows to either "spend" one until recharged for common uses (like skill re-rolls) or "burn" permanently for stronger effects (like avoiding certain death).
 * Dungeons & Dragons has numerous examples of this:
 * In the Forgotten Realms setting during 2nd Edition certain clerics of Tymora, the goddess of luck, have the granted power to re-roll a die once per day. Similarly some clerics of Beshaba, goddess of misfortune, have the ability to force enemies to re-roll their dice.
 * "Fatespinner" Prestige Class from D&D 3.0 Tome and Blood (updated in Complete Arcane) has a primary ability allowing to shift around good and bad luck, as well as the Fortune's Friend, where having supernatural good luck and unlikely events is a class feature. Neither are very powerful but they are hella fun to use.
 * Complete Scoundrel'' D&D 3.5 supplement introduced a line of luck feats. Each feat increased the number of times per day you could re-roll a die by one, and also added a new circumstance under which they could be used. Of course, the useful feats all required having a bunch of less-useful feats as a pre-requisite. You basically had the choice to either sink all of your feats into luck to try and get something useful out of it, or ignore that it ever existed and pick up a number of minor bonuses with normal feats(+1 to hit, +3 to a skill check, +1 HP/level, etc).
 * The Dark Sun campaign setting in 4th edition suggests an optional rule that allows a player the choice to re-roll the d20 attack roll whenever they originally roll a "1" (indicating a "critical miss"). The new die roll must be accepted, however, and if the result is a 5 or less the character's weapon breaks.
 * The Elf race in 4th edition has an innate power that allows the player to re-roll a single attack roll during an encounter, though they must accept the second result.
 * Most leader-type classes in Dungeons & Dragons 4th edition have powers that allows one to do this, such as the Bard's Unluck which allows him to swap an enemy good roll for a bad one and a friendly bad roll for a good one. In fact, The Virtue of Prescience build for Bards is BASED AROUND LUCK/FATE MANIPULATION. Halflings have the power to force an enemy to re-roll a hit.
 * In 4th Edition Eberron, the Dragonmark of Detection allows one to roll twice on perception checks and pick the best result.
 * Pathfinder features the Persistent spell feat which can modify a spell so that the target has to save against it twice. Especially effective with multiple targets.
 * It also has the witch's fortune and misfortune hexes, which allow you to roll twice and take the best result, or force you to roll twice and take the worst result.
 * Early editions of Shadowrun had the Karma Pool, which allowed a character to re-roll dice for failed tests, buy additional dice for a test or even buy successes directly. 4th Edition calls it Edge.
 * In Earthdawn the Horrors of had this ability: their "cursed luck" power could change a certain number of dice from whatever they rolled into "1"s. The Dragons had a lesser version of this power that only forced the player to re-roll his dice.
 * Most species in Star Wars Saga Edition have the ability to roll a single skill twice and pick the best result.
 * In West End Games' Star Wars game, a character could spend Force Points to double his skill and attribute codes, which greatly increased his chance of success.
 * Cthulhu Tech has Drama Points. Spending them adds to your dice pool or subtracts from your opponent's dice pool.
 * In the Buffy the Vampire Slayer RPG, Drama Points can be used to increase the chance of success for Heroic Feats.
 * Dreamblade, a short-lived WOTC miniatures game, had an ability called Fortunate which let you re-roll attack dice as well as one called Rewind that let you re-roll your initiative die.
 * Warhammer 40,000 is loaded with them. The Twin-Linked rule allows re rolls with missed shooting attacks. Master crafted allows one re-roll per weapon in close combat. Preferred Enemy allows rerolls in close combat. The psychic powers Doom (inverted example that harms enemy luck), Fortune, Guide, and Warp Time all allow re-rolls.
 * In Battlefleet Gothic it became a part of regular mechanics - the main (and often the only one) mechanical attribute of a commander is number of re-rolls for Leadership checks granted to the subordinate units.
 * The Hatred special rule in Warhammer Fantasy Roleplay functions like Preferred Enemy above. The Always Strikes First special rule when combined with base initiative being faster than an enemy works in a similar fashion.
 * In Warhammer 40,000 Roleplay PC and significant NPC have Fate Points, which allow reroll or one-shot bonus and work as limited Plot Armor. They can be spent or burned (though even if PC avoids a messy overkill, usually this doesn't equal "no scratch", but "needs medical care and some bionics"… unless the PC has a specific talent, in which case it's explicitly a miracle). Sometimes the Fate Points total is used as Luck Stat. Aside of the common uses, some classes and talents open new ways to spend them — mostly mastery type talents ("spend FT instead of testing the [prerequisite skill] and automatically get degrees of succeed equal to the Characteristic Bonus") and Pure Faith tree talents ("spend FP to [perform a minor miracle], burn for the greater version"). The system will eat those fate points up even if you don't have a Killer Game Master; someone with a 60 in a skill is one of the best in the sector at that thing but will still fail well 40% or more of the "challenging" grade tests they have to make without additional advantages (really good tools, etc). Combat is a rare exception as it's easy to get plenty of bonuses from choosing tactics well, but your enemies can do the same. Lethality ensues.
 * In Black Crusade Infamy points work much the same way for the Heretics. It's possible to accumulate much more, but Infamy is used for many other things, up to deciding whether the character will wind up as Daemon Prince or Chaos Spawn upon accumulating 100 Corruption points, and dodging death costs much more, so while they're easier to gain, burning some still hurts.
 * In The Dresden Files RPG, you have the option to spend a Fate Point in order to reroll all the dice in a given exchange if you really blow the roll, or your opponent rolls exceedingly well. This is meant to represent the character's mortal free will asserting itself.
 * This is the purpose of the Probability Control power in Hero Clix.
 * GURPS has multiple levels of the Luck advantage, which grant a character the ability to reroll, with the frequency dependant on what level it was purchased. The base version allowed for once per session, and the highest level allowed a player to do so once every ten minutes of gametime. And these could be purchased along with Super Luck, which would, once per session, allow the player to instantly declare a success on an action.
 * Mutants and Masterminds has had Hero Points in all three editions, which can be used for rerolls that are guaranteed to be better than average. Also, since 2nd edition, characters can buy the Second Chance feat which allows them to roll twice and pick the higher number for a given narrow task.
 * Feng Shui has the Fortune stat, which you can spend points from to add a positive die to any roll. The Everyman Hero has the most of any character archetype, and he or she can make Fortune rolls as if he or she had the full amount of points, no matter how many points he or she spends.
 * Weapons Of The Gods has "Joss", which can be used to add dice to your rolls, or to take dice away from an opponent's.
 * Exalted has several versions of this. Most Exalted have access to a Third (something) Excellency, which lets them re-roll on a failure. The Sidereal Exalted have several varieties of this, as befits their office as Fate Ninjas. For example, they can cause long-term bless/curse effects on other people by manipulating Astrology, and they can change what numbers on their dice count for success.
 * Mage: The Awakening has the Fate-arcanum, which is involved with luck and messing with destinies.
 * The Lord of the Rings Strategy Battle Game has Might, Will and Fate points, which nearly all the named characters and generic leaders get. The first two can be spent in order to modify certain dice rolls, whereas Fate points are spent to give a character a one-in-two chance of avoiding taking damage they would otherwise have suffered.
 * Adventure! has Inspiration, which, in the grand pulp tradition, can be used for "creative editing." "Oh, we crashed fifty miles out from Tripoli in the middle of the desert? I know a guy in the French Foreign Legion who set up shop in a small village fifty miles out from Tripoli! It might be a day's hike east..."
 * Deadlands had a Luck Manipulation Mechanic that could be invoked by spending "Fate Chips"—actual, real-world poker chips the players and GM draw blindly—to amend the results of particularly unfortunate dice rolls. Many Arcane Backgrounds have extensive Fate Chip Manipulating Mechanics, to add further robustness. The particulars would require a long-winded explanation, but the generalities live on in a more general ruleset made by the same company, Savage Worlds.
 * In Paranoia's latest edition, Perversity points are a combination of this and Experience Points. On skill rolls, they can be used to push someone's chances to succeed in an activity up or down. However, spending them to force a fellow Troubleshooter to fail a skill roll is a treasonous waste of Friend Computer's resources, and is punishable by termination and erasure. Have a nice daycycle!
 * Swashbucklers of the 7 Skies has "style dice," which are earned for acting in genre or otherwise entertainingly and constructively. They net a player extra dice for rerolls, or flat +1 bonuses to any roll (useful when you need just a little more but a reroll is more likely to harm than help). There's a limited pool of style dice available which replenishes as they're used, meaning players are encouraged to not only act outrageously to acquire extra dice but spend them like water (usually on said outrageous actions) to keep the dice flowing.
 * Alternity has "Last Resort Points" that can be spent to change result of a check in which the character is involved by one grade (i.e. improve one's own Failure to Ordinary Success or Critical Failure to simple Failure, or degrade an opponent's Amazing success to Good), if it was normally possible. Alternity 2017 has "Hero Points", spent to modify result of a skill check (one's own or an opponent's) by adding or subtracting a randomized value.
 * Luck points in Arrghh Bottom Sound can be spend on re-rolling any roll the player made (or another player, if the characters are present). Luck points are not recharged and only received when a character gains a growth point.
 * FATE uses… surprise… Fate Points, as the flexible adjustment mechanics.
 * Fate points mostly work with Aspects: "Game" (setting flavors, general circumstances), Situation (features of the environment, placement, temporary character effects, thus may affect the whole scene or specific characters: "Sniper Perch", "The Street is Noisy", "Covered in Slime"), Character (traits, ties, status, goals, etc — "Tempted by Shiny Things", "Taught in the South-Western Fencing School", "Ancestral Sword", "Avenge My Father"), Boosts (minor short-term advantages, often "spare change" of skill use, invoked for free once: "Running Start", "Has a Plan") and Consequences («lasting injuries or problems that you take away from a conflict: Dislocated Shoulder, Bloody Nose, Social Pariah»).
 * Fate points can be spent to:
 * Invoke an aspect (unless free; not necessarily the Character's own — "X is tempted by shiny things, and will be easier to persuade if…").
 * Power a stunt (variable cost, usually extra effect for a skill: «Backstab: You can use Stealth to make physical attacks, provided your target isn’t already aware of your presence»).
 * Refuse a compel (from Aspect: "I'll resist the temptation of a shiny thing this time").
 * Declare a story detail (add something to the narrative based on one of the PC's own aspects).
 * Fate points are automatically refreshed to a certain value per session, but there are always other ways to earn Fate Points:
 * Accept a Compel ("I'll… try to steal that shiny thing").
 * Have your aspects invoked against ("They tempt me by that shiny thing"; ­the opponent spends FP immediately, the character gains it at the end of the scene).
 * Concede a conflict ("ya got me fair and square"), extra point per Consequence attached.
 * The game balance usage is having 1 Fate Point per PC, distributed between the participating NPCs as GM sees fit; they can earn more (via Compel).

Video Games

 * Arcanum has fate points, which may be used to force a critical success (or do something else if you prefer).
 * Billy vs. SNAKEMAN has this in a few areas.
 * BillyCon's Cosplay minigame lets you reroll once per level of Combat Sewing you have.
 * High level opponents in Mahjong and Flower Wars can redraw cards to make them more formidable. You can do the same, but doing so causes you to lose your "No Cheating" bonus, and puts you at risk of getting caught cheating.
 * Once per Zombja map you can break Rule 17 and "Be a Hero", automatically giving you the best rollable result for one attack.
 * "This Fist Of Mine" does the same thing with Worldkai, but with a stamina cost instead of a frequency limit.
 * "Escape Jutsu" lets you reroll what Mission you're assigned, and "Sight Beyond Sight" forces your next Mission to be the same as your last one.
 * Heroes of Might and Magic V has an ability that adds an extra roll for all luck-based abilities.
 * Call of Duty Black Ops: The "care package" killstreak is a random drop of any of the other killstreaks, plus the nearly worthless box of ammo. The Hardline Pro perk allows players to "re-roll" those care packages to try their luck again.
 * The Binding of Isaac features an (incredibly hard to get, but extremely powerful) item that works like this. It is the, which allows you to transmute power-ups & activated-items into another random item of either kind. This allows to try to swap Powerup Letdowns or Mutually Exclusive Powerups for something potentially more useful for your current playthrough.
 * Unlimited Saga, as part of its attempt to create the feel of playing a Tabletop RPG, has something similar in concept to this: it's replaced the endless literal dice rolling of a Tabletop RPG with spinning reels that the player stops by pressing a button, giving the player some degree of control over the outcome. Which just makes it even more frustrating when you get a bad result.
 * Final Fantasy Crystal Chronicals Crystal Bearers has artifacts (ring, earring, and "accessory" items) that effect all of your skills, including Luck. Luck is mainly used for what items drop when defeating enemies, or whether they drop anything at all.

Web Comics

 * Darths and Droids has a mention of the "Fate Manipulation Re-roll" Jedi power. Jim's misunderstanding of how the rule works turns out to be important: he refrains from using it at first because he thinks it refers to re-rolling in-game dice. Later, confusion over how to interpret this power's "one use per day" restriction when interplanetary travel is involved contributes to Qui-Gon Jinn's death. Much later, Annie uses a re-roll to help Anakin survive Pete's factory sequence.
 * In Homestuck,  Vriska literally has the ability to manipulate luck in her favor—such as rigging a coin flip to land in her favor or stealing her enemy's luck, causing it to fall through the floor.
 * She suffers an  because of this:   flips a coin to determine her fate. Vriska predictably manipulates the outcome and leaves - only to   because the toss didn't actually matter.