Standard RPG Items

Note: Feel free to split parts of this article once they have acumulated a sufficent amount of examples. It might be a good idea to take them to YKTTW first though.

This is basically a list of the generic item types you'll find in a CRPG;

An item to cure each of the Standard Status Effects. This includes antidotes for poison, cures for paralysis, cures for sleep (although most games allow sleep to be cured if the victim takes damage), cures for being turned to stone and so on.
An item which cures all status effects. Usually rare and/or expensive at the start of the game, but becomes trivially easy to stockpile by the end.
An item which heals Hit Points. See Heal Thyself, Healing Potion and Health Food for examples. There may be progressively more powerful versions of the item, to be useful at higher levels of the game. This may go for two or three tiers, up to an item that heals all hit points.
An item which heals Mana Points, or the game's equivalent, and the more powerful versions.
An item which heals both HP and MP, usually up to the max of both. Often an unpurchasable rarity, in which case see Emergency Energy Tank.
Items which revive Only Mostly Dead characters. Often with different versions which revive the target with ever increasing health.
Items which replicate the effects of spells.
- Single use items which can damage enemies (but don't specifically cast a spell).
- Weapons or Equipment that cast a spell or other form of Special Attack when used as an Item.
Items which permanently boost a character's level or stats.
Items which temporarily boost stats.
An item or spell that wards off Random Encounters.
An item or spell that increases the amount of Random Encounters, or even calls them up on the spot.
Mass effect versions of any of the previous. IE, a cure potion that can be used on the entire party in one character's turn.

In addition, most RPGs feature a Warp Whistle and/or Escape Rope to allow quick travel/teleportation to or from towns or dungeons.

Examples of Standard RPG Items include:

Examples of individual status effect cures

Pokémon plays this straight; the sequel includes berries which can be attached to Mons, to activate as soon as they are needed.
The Final Fantasy series has loads. For instance, the Golden Needle / Soft Potion cures petrification.
- Some of these items toggle a Standard Status Effect. Using such an item on a character without that status will give them the status. Occasionally this will be useful, or even mandatory. III, notably, has some rather infamous dungeons that require your entire party to have Mini status.
- Status-toggling items can usually be used on the enemy as well, making them useful both for curing your characters and for attacking.
- In some games, certain monsters will take damage or suffer instant death when a certain status-curing item is used on them. For instance, using a Golden Needle / Soft Potion on a stony or statue-like monster in V will hurt it, as a helpful NPC will tell you.
The Mario RPGs
EarthBound, with its more modern varieties of Standard Status Effects, has cold remedies that cure the common cold, and wet towels that cure sunstroke.
SaGa Frontier
In Nethack delayed action petrification can be cured by ingesting anything which is acidic, which for some reason includes lizard corpses, which conveniently never rot away like other corpses do.
- Lycanthropy can be cured by eating a sprig of wolfsbane or drinking holy water.
Dis-X (where X is the condition) in Shin Megami Tensei games.
The Dragon Quest series has antidotal herbs, which cure poison, and moonwort bulbs, which cure paralysis. Dragon Quest VIII and Dragon Quest IX added upgraded versions of these items that restore HP in addition to curing these status ailments.

Examples of multiple status effect cures

Full Heals and Lum Berries from Pokémon
Various examples from the Final Fantasy series
Refreshing Herbs from Mario & Luigi
Snake Oil from SaGa Frontier
Tasty Tonic from Paper Mario
Break Free inspirations in City of Heroes
In Nethack using a Unicorn horn will cure all status effects except for polymorphing, lycanthropy, delayed petrification and delayed turning-into-slime. However, any individual use of a horn isn't guaranteed to work, so having a unicorn horn isn't proof against status effects causing a game over.
The Tales (series) has fruit-flavored Gels/Gummy. Apple and Lemon heals 30% and 60% HP.
EarthBound has Refreshing Herbs, which cure most status ailments. Secret Herbs, Cups of Lifenoodles, and Horns of Life, although usually used to revive unconscious characters, can also cure pretty much every status ailment in the game.
Limes in Dubloon. They aren't even as neccessary since status ailments are cured instantly after a battle.

Examples of magic/tech point restoring items

Ethers from Final Fantasy
Ethers and Elixers from Pokemon. Due to Pokemon moves using their own PP, Ethers and Max Ethers only restore PP for a specific move, while Elixers and Max Elixers restore PP for all moves.
Syrup and Honey in Super Mario RPG
Catch a Breath inspirations in City of Heroes
Among others, Garlic Water from Disgaea
The Tales (series) has fruit-flavored Gels/Gummy. Orange and Pine heals 30% and 60% TP.
"Chakra" or "Soul" items in different Shin Megami Tensei games.
The Dragon Quest series has magic water, and more recently, sage's elixirs. Prayer rings also restore MP, but have a limited number of uses.
The EarthBound series has plenty. MOTHER 1 has PSI Stones, EarthBound has Bottles of Water, PSI caramel, Magic Truffles, and others, and Mother 3 has magic pastries.

Examples of HP and MP healing items

Dragon Age: Origins had mages drink Lyrium Potions for restoring mana, stamina draughts for warriors and rogues, and everyone could drink poultices for restoring health (... a moist cloth bandage. As some lines from characters low on health ask for bandages, perhaps either the animations or the naming of poultices were a discrepancy that never got fixed.). 2 calls the health restoring items the conventional term "health potions".
Elixirs and Megalixirs from Final Fantasy. Megalixers actually heal all of the party members currently in combat.
Various types of cake and mushrooms in Paper Mario.
The Tales (series) has Melange Gels, which heal 30% of both HP and TP, and Miracle Gels, which heal 60% HP and TP. Also, Elixirs heal both to full.
In Shin Megami Tensei games, Muscle Drinks, Soma Drops, and Soma.
- Muscle Drink increases your max HP for that battle. Fuck Yeah.
Pokemon has Potions (20 hp), Super Potions(50 hp), Hyper Potions(200 hp), Max Potions(Max hp) and Full Restores(Max hp + Cures all status effects), plus a variety of other healing items. It also has Ethers and Elixers, which recharge the PP(mana).
Dragon Quest standards include medicinal herbs (HP) and magic water (MP). They also sometimes feature Yggdrasil dew, a rare item that fully recovers everyone's HP. Later games in the series feature more restorative items.
EarthBound has too many to count. Most of them are real-life foods, too.

Examples of items which revive downed characters

Revives and Max Revives from Pokemon
Phoenix Downs from Final Fantasy
Life Shrooms from Paper Mario
- And 1-up mushrooms from Mario and Luigi
Life Bottles from the Tales (series)
Awaken inspirations in City of Heroes
Revival Beads Revival Gems, and Balm of Life in Shin Megami Tensei games.
Amulet of Lifesaving in Nethack. As a single character game, this is your only 'get out of stupidity free' card.
Horns of Life in EarthBound and Cups of Lifenoodles and Secret Herbs in EarthBound and Mother 3.
Yggdrasil leaves from the Dragon Quest series. You can usually get them for free late into the game, but you can only carry one at a time unless you find one in a treasure chest.
Rum in Dubloon.

Examples of spell replicating items

Many examples in Final Fantasy, such as the Magic Lamp that casts a random summoning spell.
As well as Golden Sun
The Elder Scrolls goes as far to allow the player to make their own in the form of enchanted weapons and potions.
Skies of Arcadia has boxes that cast spells. Rather than having a number of charges, boxes have a chance of breaking every time they're used.
- Technically, however, many items in the game fall somewhere between this and the standard restoration categories. Basic healing crystals cast the same spell on the target as the basic green magic spell and both always heal 500 HP. Same goes for status effect crystals/spells and kind of for revive crystals/spells except the spell has a 50% failure rate while the crystal doesn't.
Pokedolls (from Pokemon, natch) have the same effect as Roar or Whirlwind. The equippable item Smokeball guarantees an escape from battle if the Pokemon holding it is battling.
In Roguelike games wands and scrolls replicate the functions of many spells.
"X Rocks" "X Gems", and sometimes "X Magatama" each cast a specific spell in Shin Megami Tensei games.
Seiken Densetsu 3 has items for most spells to account for all the possible party setups. No group need go without healing, stat-ups or elemental weapons.

Examples of single use offensive items

Rock Candy in Super Mario RPG
Many examples in Final Fantasy. Most interestingly, the Ninja's "Throw" ability in many games lets them turn any inventory item into one of these.
As well as Golden Sun
And the Tales (series)
The Dizzy Dial, Fire Flower and POW! Block, among others, from Paper Mario.
The magic stone item in SaGa Frontier
In Nethack potions with negative effects can be thrown at monsters; if the bottle hits and spills its liquid on the monster it will get whatever negative status effect drinking it would have caused.
- Also, you can throw cream pies at monsters, with the Cream Pie in The Face temporarily blinding them. The Dev Team Thinks of Everything.

Examples of usable weapons and equipment

Most weapons/items with an Elemental Affinity in Shining Force (Also Halberds). However, using them too many times would cause the weapon to destroy itself. Fortunately, the game would warn you when the weapon was on it's last use, and you could have it repaired.
Staves in Lunar Silver Star Story Complete. In Eternal Blue Complete, the devs realized there was no reason to use the item's regular attack, and so switched the attack to these.
Every object in Phantom Brave. Not just weapons, but loaves of bread, vases, rocks, trees, fish, clumps of grass, crates, and more. Otherwise, the game pretty much averts this trope with no inventory items at all.
The Dragon Quest series has plenty of these.

Examples of items which Buff Stats

X-Items from Pokemon
A wide variety of drugs in the Fallout series could increase various stats, with a chance of addiction and withdrawal. Drug use also results in temporarily decreased stats after the effects wear off, even if you don't become addicted.
Peppers in Mario & Luigi: Partners In Time
The Power Punch, Courage Shell, and Repel Cape, among others, from Paper Mario

Aversions

SaGa Frontier has no revive item, the mechanics of the game mean downed characters can be brought back by normal healing.
- However there are special Items that can restore Life Points on the spot; in the earlier two SaGa games, those items are a bit more common In Romancing SaGa 2, the only known item that can restore Life Points can be bought from a witch for 10,000 (Max amount of money you can carry at one time). In Romancing SaGa 3 these items were mostly item drops.
Similarly, the Disgaea series has no revive items or even spells. You have to pay a healer between battles (This also means a measure of redundancy in your force is recommended, in case someone gets killed in an Item World run).
The Elder Scrolls series tends to have diverse items; although potions are most often of the restoring kind, it's possible to create potions and enchanted items with (almost) any effect, provided you can find 2 (often rare and expensive) materials with the same effect (and such a pairing may have a negative effect appear twice, applying it to the potion), down to summoning an Infinity+1 Sword from Hammerspace.
- Or increasing your intelligence (and thus ability to make potions) then drinking it and makeing another and so on, until your potions are Game Breakers
  - This is capped in Oblivion, so you can't get something completly gamebreaking... just mostly. Unfortunatly a couple effects (Vampirism, and the Conjuration school spells) are gone from the alchemy lists in Oblivion.
In Devil Survivor and its sequel there are zero items to be had. Battles tend to be pretty short and if you don't have any demons or humans with skills to heal the damage and ailments too bad.
Xenoblade Chronicles has only one category of usable items - those which change the party's Relationship Values. Healing and buffing can only occur during battle, or the automatic regeneration of health between battles. So, if you ran into a trap with little or no healing on your chosen threesome...

Subversions

Final Fantasy XI has many of these items, but after about ten or twenty levels the effectiveness of most of them are too small for the cost and inventory space to justify using besides healing Standard Status Effects, and the other ones that are worth using are either drops from endgame monsters or stupidly expensive to craft, making those last resorts only. Worse still, using many of these items invokes the universal cooldown timer for a few precious seconds, preventing you from taking any action aside from continuing to auto-attack. Oh, and Phoenix Downs? They don't exist. Alchemy Needs More Love.