Dungeons & Dragons/YMMV

Assassin

 * Lawful Evil, Neutral Evil, or Chaotic Evil: Traditionally, assassins must be evil.

Barbarians

 * Neutral Good, Chaotic Good, True Neutral, Chaotic Neutral, Neutral Evil, Chaotic Evil: All alignments available to 1st through 3rd Edition barbarians.

Bard

 * Game Breaker: The exclusive spell Glibness - a +30 to Bluff checks. Can turn the Bard into a Lethal Joke Character by making any outrageous lie believable.
 * Neutral Good, Chaotic Good, True Neutral, Chaotic Neutral, Neutral Evil, Chaotic Evil: All alignments available to 3rd Edition bards, on the theory that lawful people can't be creative enough.
 * True Neutral: In 1st Edition, to become a bard, one needed to take levels in druid first. Since all druids had to be True Neutral, by extension, so too were all bards.

Cleric / Priest

 * Game Breaker: So much so in 3.5 that CoDZilla (a portmanteau of "cleric or druid" and "Godzilla") used to be a subtrope page.

Druid

 * Game Breaker: See the cleric.
 * Neutral Good, Lawful Neutral, True Neutral, Chaotic Neutral, Neutral Evil: all alignments available to third edition druids.
 * True Neutral: Prior to 3rd Edition, all druids had to be this alignment.

Monk

 * Tier-Induced Scrappy

Paladin

 * Lawful Good: Paladins serve the gods of good, and must maintain this alignment. Between Unearthed Arcana and Dragon Magazine however, variants do exist for alternate alignments.
 * Lawful Stupid: Unfortunately, many players play this alignment when playing a paladin.

Ranger

 * Lawful Good, Neutral Good, or Chaotic Good: 1st and 2nd Edition rangers had to be of good alignment. 3rd Edition rangers could be any alignment.

Wizard / Magic-User / Mage

 * Game Breaker: At high-level power play, a straight wizard played by a sufficiently Crazy Prepared player is considered to be the most powerful class in the game. While they're more fragile than clerics and druids and can't tank, the arcane-exclusive spells (like Teleport) make up for it.

Archivist

 * Game Breaker: Its spell mechanics are similar to a Wizard (a Game Breaker in its own right), and it has access to every divine spell (Clerics and Druids manage to be incredibly powerful with more limited spell lists). And the class has some useful abilities on the side. Every bit as potent as its fellow full casters. Not to mention, you can take Mystic Theurge (advances casting in two spellcasting classes) with both class's spellcasting tied to Intelligence, the most useful mental ability score.

Ardent

 * Ensemble Darkhorse: Because of how well-balanced and unique it was, the Ardent was one of the few fondly-remembered things about Complete Psionic.

Binder

 * Ensemble Darkhorse: Fandom find the other 2 classes in To M to be awful, if not impossible to use. The Binder however is considered to hit the "Powerful enough to be fun to play, but weak enough to not be a Game Breaker", and easily one of the most supported non-core classes by homebrew (possibly the most outside of Tome of Battle).

Crusader

 * Base Breaker: By virtue of being a Tome of Battle class.

Divine Mind

 * Tier-Induced Scrappy: A very poorly designed class, even from a flavor standpoint.

Erudite

 * Game Breaker: It's one of the Big 6, and stands as one of two members of the Big 6 that can use both Arcane and Psionic abilities (the other being the Psionic-variant Artificer). The Erudite is nearly unmatched in flexibility, as you are able to spontaneously manifest any power you know (though there is a debate on how this is supposed to work due to poor wording).

Healer

 * Tier-Induced Scrappy: Due to its limited ability to do anything but heal, Healers tend to get a poor reputation.
 * Rescued from the Scrappy Heap: Giving them access to Sanctified Spells from the Book of Exalted Deeds gives them a fair amount of additional options in combat other than healing (which is perfectly legal by the rules of Sanctified Spells, as Healers are all good-aligned spellcasters who prepare their spells).

Incarnate

 * Chaotic Neutral: One of the four possible choices for an Incarnate character, and the weakest of the four (ranged-focus, but the developers kinda screwed up here).
 * Lawful Neutral: One of the four possible choices for an Incarnate character, and the one closest to being a frontliner.
 * Neutral Good: One of the four possible choices for an Incarnate character, can be played as a tank or as a psuedocaster via Use Magic Device. Has the best defenses this side of a Full Caster.
 * Neutral Evil

Lurk

 * Tier-Induced Scrappy: While it is a Rogue with psychic powers, the Psychic Rogue is considered better due to not having class features that rely on Psionic Focus. This class is still pretty good, but most people will point you towards the Psychic Rogue.

Psion / Psionicist

 * Complete Monster: Psions have a number of unique ways to pursue a career in this field.
 * Ever wanted to permanently turn someone into a physical and mental clone of yourself? Slowly and gradually, over the course of a week or so?

Samurai

 * Tier-Induced Scrappy: The Samurai is like the Fighter, but with less options.
 * The Lawful over Good trait was another popular class feature.
 * Even worse: A TW Fing Ranger outclasses a Complete Warrior Samurai. At least the Oriental Adventures one was decent!

Shadowcaster

 * Tier-Induced Scrappy: The early levels are murder on a Shadowcaster. They aren't too powerful late-game either, but they are still capable of contributing to the party.

Soulborn

 * Tier-Induced Scrappy: It ends up being the worst of the three Meldshapers. It's even weaker than a Core Paladin!

Soulknife

 * Tier-Induced Scrappy: Because you can't enchant a Mind Blade like you can a physical weapon, a Soulknife tends to do less damage than a fighter of equal level.
 * Also, see Samurai, "less options". Having the Whirlwind Attack feat without the ridiculous prerequisites is neat, though.

Swordsage

 * Base Breaker: By virtue of being a Tome of Battle class. It's also the most overtly pseudomagical of the three, so haters who know what they're talking about hate the Swordsage the most.

Warblade

 * Base Breaker: By virtue of being a Tome of Battle class.

Battlemind

 * Tier-Induced Scrappy: The way Blurred Step and Mind Spike originally worked didn't make the battlemind a very good defender. This has been mostly relieved with the July 2010 errata.

Creatures

 * Adaptation Displacement: Compare how many series' portray Bahamut and Tiamat as dragons. Now look up their origins.
 * Complete Monster: Pretty much all of the Demon Lords. Special mention goes to Lolth.
 * Graz'zt is the Faux Affably Evil demon lord of hedonism and other such things (and somewhat appropriately keeps a large slave harem), and runs an empire that basically revolves around torture and slavery. Demogorgon is an Ax Crazy maniac. Orcus is a god wannabe who wants to turn the afterlife into hell For the Evulz. They're all pretty much the same.
 * Chaotic evil dragons come across as somewhat more evil than the lawful evil ones. Blue and green dragons, for all their faults, genuinely care about their mates and offspring (well, usually). The same cannot be said for black, white and red dragons.
 * Ensemble Darkhorse: Meepo the Kobold in 3rd Edition. This little lizard-dude, originally just a kill-it-for-stuff encounter in the adventure The Sunless Citadel, was so popular that he made an appearance as an NPC in at least one other adventure, featured in a web-exclusive article in which he became a half-dragon were-velociraptor, and got whisked away to another dimension in which he obtained a magical pump-action shotgun. Truly, Meepo is the pinnacle of koboldian awesomesauce. He even makes a cameo in d20 modern.
 * As far as races go, the Warforged from Eberron were very well received. The Shifters were also well-liked, but not as much as the Warforged.
 * As a matter of fact, these two races (and Changelings) were put in as monsters in the first 4E Monster Manual, and Shifters were introduced as a playable race in the second 4e Player's Handbook. Warforged were made playable in any setting thanks to a free(!) Dragon article on Wizards' official site.
 * Hilarious in Hindsight: The complaints about 4th Edition playing like a video game certainly won't get any better when the corebooks have a playable race called the Dragonborn.
 * Magnificent Bastard: Asmodeus, most notably. Grazz't, Dagon and Pazuzu also count.

Gaming

 * Game Breaker: Numerous in all editions, although 3rd edition is particularly famous for this, due to the sheer volume of various mechanical goodies, provided by its supplements, as well as the generally high power level of the characters. Notable in 4th edition for having at least two discovered before the game was released. Errata has fixed most of 4e's breaking stuff, but not all. Some examples:
 * Clerics, Druids, and prestige classes related to either had the best of being both linear warriors AND quadratic wizards... and aside from a decidedly lower-tier class selection, they were the only healers you could pick. If the Druid or Cleric stuck to healing, it didn't affect party balance. It was when the power gamer got his or her hands on them that it became a problem...
 * If they stick to healing, it breaks the game in the opposite direction. Attack and Damage scale up far faster the Armor Class and Hit Points in D&D. Playing a Cleric that is The Load isn't much better than playing one that that is the Game Breaker.
 * Certain builds were able to incur trillions of damage in one attack, at range. One low-level spell with a specific combination of metamagic feats would raze anything and everything in a 10-mile radius to the ground. And then there's Pun-Pun, a level one kobold with inifinite stats who can reach infinitely far, including across the planes, and can cast any and every spell an infinite number of times per day. Did I mention this kobold is more of a god (infinite divine ranks) than the actual gods?
 * Essentials. Not in-and-of themselves, mind you, and not so much if you're in an all-Essentials group, but consider the following. Prior to the release of Essentials, basic attacks were just that, basic. They were usually the weakest hitting things for damage dealers, and didn't have all the cool effects other powers did. Thus, classes such as Bards, Warlords and the like which gave out basic attacks like candy would only marginally influence the tide of battle. Now enter the Essentials, which are based around improving or replacing basic attacks: Slayers that wield 2-handed weapons that deal as much as 4 weapon damage on a single basic attack; Scouts that get granted one melee attack and are suddenly making 3 or more of them; latter additions give us Vampires that effectively become unkillable as long as they keep hitting, and the Bladesinger that adds a burst of various magical damage each time he hits. Yikes.
 * Tier-Induced Scrappy: 3.5 Monks are noted for getting many abilites that are either done better with spells gotten much quicker (over 20 levels they get the ability to reduce fall damage, that's a first level spell for a caster or 2000 gold for everyone else) and don't synergize at all (Monks have one ability that makes them move fast, and another that requires them to stand still) to the point that when asked to optimize a Monk, most suggestions are to play another class. Truenamers also get a lot of flack for getting weaker as they level up as they need to meet an (already hard check) with a requirement that goes up by 2 each level, but you only get + 1 to make the check a level (Soulknife and CW Samurai also fall into this for similar reasons, but Monk gets the worst because it is "core" and part of the base game and truenamer is just that... Egregious).
 * Complete Warrior Samurai deserves special mention in that is the absolute lowest Tier. In original outline of the various Tiers, CW Samurai is so low that it is actually ranked lower than Expert, an NPC-only class with versatile skill selection and no class features. There is literally nothing that a Samurai can do that a Fighter (already considered one of the lowest tiered classes) cannot do better while simultaneously doing many other things better than the Samurai.
 * Most of the Far-East themed classes from the Complete series were this way. Shugenja had incredibly limited spell selection to the point that the player chose very little of his character's core abilities. The fact that they were Divine casters (and thus able to cast in armor) was negated by their lack of armor proficiency and by having the worst Base Attack Bonus in the game (for comparison, most Divine casters get the medium Base Attack and medium or heavy armor proficiency). Wu Jen had weaker casting than wizards, and their "Spell Secret" class feature left them Blessed with Suck as it gave them free metamagic feats at the cost of crippling RP restrictions (each one came with a "taboo" that shut off the character's spell casting for the day if violated. And the metamagic feats weren't even the good ones!), meaning it holds the dubious honor of being the only class where Prestiging out is the only way to avoid crippling drawbacks.
 * Every freaking class in the 5e playtest is subject to his. Clerics have been reduced to useless healbots, and Rogues and Fighters have been made completely and utterly worthless. Wizards are the high-tier version of this trope since they're the only ones who actually can survive a fight. Apparently, the reason Wizards are so over-powered in the playtest is because Mike Mearls encourages the Fandom Rivalry between close combat classes and spell-slinging classes when he claimed "fighters are for morons, Wizards are for smart players."

Items

 * Good Bad Bugs: Most rules exploits have been hilariously exploited with purpose built characters. These range from the "unintended but not game altering" (Because alcohol is a poison in the game's terms, an ability with the effect of "save against poison for bonuses" gets activated by booze) to the countless much worse ones.

Meta

 * Adaptation Displacement: In Japan, if you mention D&D, most people will probably sooner think of the Capcom Beat Em Ups mentioned below than the original tabletop game.
 * And the Fandom Rejoiced: In early 2012, Wizards of the Coast announced that they would be reprinting the core books for the first edition, with funds going towards building a statue of Gary Gygax.
 * Broken Base: The edition war between 3rd and 4th editions. While there were some changeover gripes between 2nd and 3rd, this edition war has reached Internet Backdraft levels, possibly simply due to the availability of the Internet and the increased popularity of the system. Also the setting issue, where assorted players have flame wars over pointless gripes such as whether Eberron's Dungeon Punk setting is bad or not.
 * And, more recently after WOTC released a new set of core books called "Essentials", there is a heavy flame war between people who like "pre-E" D&D and those who like "post-E". The former group tends to call this new set "4.5", the latter gets positively enraged at seeing this number.
 * And with a new edition just being announced, you can bet your sweet bippy the edition wars will begin anew...
 * They already have: Fans of 3E are rejoicing over 5E, while fans of 4E are crying Ruined FOREVER at the return of Linear Warriors, Quadratic Wizards.
 * It Got Worse: Many of the rules just don't make any goddamn sense in the playtest, such as having to roll 36 hit dice for a rat swarm because the game treats each rat as an individual monster. And remember Linear Warriors, Quadratic Wizards? Well, let's just say the problem's worse than ever: Rogues and Fighters are absolutely worthless and Clerics have been reduced to healbots. The kicker? Wizards can do everything better than all the other classes combined. A lot of longtime fans who have accepted the move to 4E hate the playtest as well, and even some 4E haters are crying out that Wizards seems to have taken only the worst parts of all the previous editions to make the game. About the only reason the base is broken over it is because of 4E's Hate Dumb loving it blindly without even caring about how badly-designed the game is.
 * Complaining About Games You Don't Play: Considering that this is a game with its rules spread across as many as six different editions, with extra supplements for almost anything, a monthly publication that provided extra rules and modules, and that this is a gaming hobby where most people internalise the identity of the game they love, it's very common to find people complaining about whole editions of the game they've never played, never read, or in some cases, never heard of outside of the complaints of others. In the information age, the most noticeable version of this is the reaction to 4th Edition's latest extra rules supplements, but it goes back further than that. Especially given how complex some rules supplements are, it's pretty much inevitable that people will disallow some based on no actual play experience. This can make it awfully awkward to deal with legitimate concerns about any particular part of the game, since there's a lot of backdraft over disliking things other people like.
 * Fandom Rivalry: Some fans of weapon-using classes (I.E. Fighter, Ranger, Rogue, Barbarian, Paladin and Monk) don't get along with some fans of magic-using classes (I.E. Wizard, Sorcerer, Cleric, Bard, Druid and Warlock). Mike Mearls encourages this.
 * Fanon Discontinuity: Every edition has inspired Fanon Discontinuity. There is still a very vocal 2nd Edition fanbase that despises the changes wrought in the transition to 3rd, and not a few 1st Edition holdouts who consider 2nd to be a bastardization, and a handful of hardcore grognards who think 1st Edition should never have supplanted "classic" D&D (called it 0E [Zero-E]). The 4th edition gets it the most, and most fans couldn't stand the new alignment system. Players naturally gravitate towards the things that make them more comfortable. Of course, it's not like the books stop working when a new edition comes out, and any really cemented group is going to have lots of house rules anyway, so it's natural that players will remain players, even when they stop buying the new material.
 * Informed Wrongness: The creation of undead is regularly noted as evil, but it never really detailed what is wrong with creating a non-sentient being through the direction of energy - it just states that anything using negative energy is automatically evil. It gets even worse when golems (which require the enslaving of a sapient being) never have their creation demonized.
 * Internet Backdraft: Just try to say anything against or in favor of 4th Edition on a D&D forum, only do so if you have a death wish. Starting an argument against or for a particular setting is also ill-advised.
 * Paranoia Fuel: So wait, most (if not all) of the stars are Eldritch Abominations that want to eat us? And some of them can create avatars of their powers called Star Spawn?
 * Retcon: 4ed recently had a relatively minor one concerning the war between the Gods and Primordials.
 * Spiritual Licensee: Krull was going to be an official D&D movie, but lost the license partway through development.
 * They Changed It, Now It Sucks: It has happened for every edition change. Some might argue that 4E most of all, but veteran D&D players would point out that it only seems that way due to the much wider availability of the Internet. Interesting to note is that this is now happening WITHIN 4th Edition itself. Wizards has started to release errata/updates every few months, usually to stop overpowered exploits (although sometimes for other purposes too). Naturally, people have either declared it to be the best thing since sliced bread, or threatened to stop playing D&D. And with a new edition in the works, expect to see this yet again!
 * Unfortunate Implications: You have your elves. They're Usually Chaotic Good. Then you have your Drow. They're evil and black and the women are in charge. Exclusively Evil races in general fall straight into this, so let's just say that's just the start.
 * What Measure Is a Non-Badass?: 4th edition is very much geared towards heroic fantasy with the default assumption that the character is a badass, to the extent that it is mechanically difficult to create a character who is actually bad in an ability (as against 'average'). Likewise you can't really model an entirely green character who has picked up a sword for the first time as even a level 1 character can call upon fairly formidable powers.