All Beer Is Ale: Nearly every mention of beer lists it as "ale". Pretty much the only drinks available in most games are ale and wine.
All Swords Are the Same: Played to different extents in different editions. The original rules started with sets of weapons given to the classes and ended with much the same. In the pre-Advanced-D&D blue book edition, all weapons — big or small, slow or fast — did 1d6 damage. 1st and 2nd edition AD&D generally avert the trope, with large numbers of different weapons all of which require proficiency. 3rd edition restores it to some extent, only requiring proficiency for exotic weapons and drawing less of a distinction between different sorts of swords. Fifth Edition encourages this as a way to incorporate unlisted weapons, with the Dungeon Master's Guide using an example of implementing a katana as a reflavoured longsword.
BFS: Shows up here and there, particularly in 3rd edition, where it was possible for a character to wield swords created for creatures much bigger (a human wielding a sword designed to be used two-handed by giants, for example). 3rd and 4th edition has the "Fullblade", which is explicitly an even bigger greatsword, ala Berserk and Final Fantasy VII.
Blow Gun: The 1984 Dungeons & Dragons Companion Set introduced the blowgun as a 6"-4' tube. Darts don't do damage but are instead poisonous. AD&D supplement Unearthed Arcana introduces the blowgun, whose needle only does one Hit Point of damage, and is therefore only effective if poisoned.
Blow That Horn: Quite a few magic horns have appeared in sourcebooks over the years, which either destroy things they're sounded at or summon minions for their player.
Boring, but Practical: A number of magic items can shed light, have spells attached, allows for the all mighty Wish spell, and so on. There are also ones that merely increase damage & hit by 1-3, which scale pretty decently with various classes (like the Insignia of Claws being basically built for monks).
Boulder Bludgeon: In early editions, if giants have boulders nearby they can pick them up and throw them at their opponents instead of using their normal melee weapons.
Breakable Weapons: Four Shield Weapons were introduced in Dungeons & Dragons Master Set. The three larger shields have multiple blades that break during combat.
Chemically-Induced Insanity: Supplement Unearthed Arcana. The Elixir of Madness is a magical liquid that causes anyone who drinks it to go insane. If it is slipped into someone's drink, it will cause them to go mad when they drink it. The victim can be restored to normal by one of three high-level spells: Heal, Restoration or Wish.
Module I4 Oasis of the White Palm. In the Temple of Set, the PCs can find a brazier filled with violet flames. The flames don't give off heat and don't burn wood. However, if they touch living flesh, they burn it, causing serious damage.
The Continual Flame spell creates a permanent fire that doesn't burn or use oxygen and is used to make Everlasting Torches.
The Companion Set introduces the Crucible of Blackflame, a hearth at the heart of halfling strongholds that radiates cold, "unburns" ashes, and can be used to make magic kites.
Cold Iron: One of the many materials that equipment can be made out of, which also includes silver and adamantine. All editions dabbled in including a list of materials, although 3.x Edition went hog-wild with it. Certain enemies could only be damaged with weapons made from certain materials. There were even materials that armor could be made out of so that druids could use them.
#62 has "Evil dragon armors", an article on making armor out of dragon scales. Each type has specific abilities based on the dragon it's made from.
The #98 article "The Magic of Dragon Teeth", which has dragon teeth made into magical devices that could summon "dragon men" when planted in the earth.
Module WG5 Mordenkainen's Fantastic Adventure. The whip possessed by the iron golem is made out of cockatrice feathers. It retains the cockatrice's ability to petrify any creature it hits.
Dark Sun runs heavily on this. Because of the shortage of metal in the setting, bones were often made into weapons.
Crystal Weapon: Weapons can be forged from "deep crystal" that's as hard as steel and can channel the user's Psychic Powers to deal extra damage.
Cursed Item: Such items are fairly common depending on the setting. Curses can range from relatively benign like the medallion of thought projection, to downright nasty like the necklace of strangulation.
Dangerous Phlebotinum Interaction: Putting a portable hole into a Bag of Holding causes very bad things to happen, although precisely what effect results depends on which is put into which. Putting the bag into the hole sucks both into the Astral Plane and renders both items lost. Putting the hole into the bag opens a dimensional breach into the Astral Plane, destroying both hole and bag and sucking anything in a ten foot radius into space.
Death of Personality: Several artifacts can have this effect, most infamously the hand and eye of Vecna. The Sword of Zariel from the 5e adventure Descent into Avernus is notable for being absolutely bonkers powerful, but also changing your personality permanently to one fitting a Celestial without a save. At the very least, you do have to choose to attune to it.
Destroyable Items: In AD&D, items get applicable saving throws when their carrier's saving throw fails. In the third edition, getting a critical hit on a creature with a spell also critically hits an item the creature was carrying. This can lead to valuable items being destroyed without the PCs knowing they were there. And of course, if you just wanna take a smack at someone's sword, shield, or armour, you can.
Doomed Fellow Prisoner: A relatively common trope in campaigns, depending on the Dungeon Master, however, one example is Master of the Desert Nomads. If the bhuts capture the PC party they will chain all of them inside cells. Each night they will take away one of the prisoners (starting with any Non Player Characters) and eat them.
Tales of the Lance. A Frostreaver is a heavy battle axe made of ice gathered from a secret location on Icewall Glacier. One full day of above freezing temperature or 1-6 hours at warm temperatures (50 degrees Fahrenheit) causes the Frostreaver to melt.
Module Rary the Traitor. Lord Robilar wields the Blade of Black Ice, which was created by the demigod Iuz himself out of ice.
Legends & Lore.
The avatar of the Japanese deity Ho Masubi has a sword made of fire. It does 10 extra Hit Points of fire damage per hit and if the target is wearing armor, the armor must save vs. magical fire or be destroyed.
The avatar of the Hindu deity Brihaspati carries a bow that fires arrows of brilliant light that can render the target blind for 1-10 days.
The avatar of the Hindu deity Indra has a bow that fires lightning bolts that do 2dl0 points of damage and have a range of 1,000 yards.
Deities & Demigods Cyclopedia. The Native American deity Hastsezini has a lance made of fire and a bow that can shoot arrows made of fire.
Dragon magazine #127. The bow Ice Fang can create and fire arrows of ice out of water vapor in the air. The arrows do double damage against creatures that use or dwell in fire. In temperatures of 120 degrees Fahrenheit or higher the arrows have half normal range.
Gods, Demigods, & Heroes. The Norse Mythology deity Valis has a shortbow that can fire an arrow of lightning.
Enslaved Tongue: Ring of Truthlessness. The wearer must lie in response to any questions asked of them for as long as the ring is worn.
Fantastic Fragility: Destroying artifacts, which require extensive research. In Dungeons & Dragons Master Set, you can try bashing it directly, but it is highly resistant to attacks (taking only minimum damage), and it gets recalled by the immortal rather than being destroyed.
Fantastic Nuke: Several, with the Sphere of Annihilation and Staff of the Magi being among the most blatant.
"Blue on Bronze". An abstract swirl of deep blues and violets. If anyone studies the painting for 20 minutes, the painting will correctly answer any yes or no question.
"Dragonnel-by-the-Cliff". A picture of a dragonnel (monster) perched on a rocky cliff over a river valley. If a person viewing the painting says the command word "fuga", the dragonnel will leave the painting and serve them.
"The Gladiators". A large painting depicting four gladiators facing off against each other in a sand-covered arena. Anyone who passes in front of the painting without saying a password will be taken into the painting and have to fight the gladiators to the death.
"Glorindel's Gates". A set of small paintings created by the wizard-bard Glorindel. Each one acts as a Gate spell, transporting the viewer to the place depicted in the painting.
"Glorindel's Living Paintings". These large paintings each show a scene that acts as a TV picture, with things moving and changing as if they were real.
"Igraine's Portraits". Each one of these pictures allows the viewer to telepathically communicate with the subject of the painting. If the subject is dead, there is a 50% chance of contacting their soul or spirit.
"The Watchers". This work depicts a wooded area with heavy undergrowth. Anyone who looks at it carefully can see the eyes of creatures looking through the brush. anyone who looks at it for too long can have their mind transferred into that of a small woodland animal living nearby.
"Widow's Walk". This painting is of the crowded dockside of a busy port. Anyone who looks at it for 10 minutes becomes immune to all divination magic and psionics directed at him for the next eight hours.
Flaming Sword: One of the most common weapon enchantments, though Freezing Swords, Electric Swords, Holy Swords and others are also common.
Flying Weapon: Multiple examples, starting with the sword of dancing in 1st Edition.
Gender Bender: The Girdle of Femininity/Masculinity is a cursed item which permanently switches the gender of the wearer the moment it's put on. The only way to change back is to use a (very powerful) wish spell, or find another Girdle of Femininity/Masculinity. Worse, 10% of these remove all sex from the wearer.
The Warlock utility power Ruinous Phrase is flavored as uttering some words, followed by the shattering destruction of a non-magic item with 20 hit points or fewer (25+level, if the Warlock is Infernal pact).
Glass Weapon: Glass weapons can be considerably more practical in D&D. The 8th level Glassteel spell can permanently make a glass weapon as tough and strong as steel.
Glowing Gem: Certain magic items, gems with Continual Light cast on them, and the Star Stones in I5 Lost Tomb of Martek.
Gorgeous Garment Generation: In 1st Edition the Rod of Splendor could garb the wielder in magical noble's clothing - the finest fabrics, plus adornments of furs and jewels, worth 7,000-10,000 gold pieces.
Third Edition has an item that does the same thing, but with a variety of other effects.
Hand-Hiding Sleeves: In The Forgotten Temple of Tharizdun module, the PCs can find robes with very long sleeves. The robes and their oversized sleeves are useful later in an extremely cold underground area the party must explore, because if their hands are exposed, they'll get frostbite.
Hand of Glory: The Hand of Glory from the 3.5 edition can be worn around the neck (presumably not alight). It provides an extra place to wear a magic ring along with being able to cast a few spells.
The Heart of the Abyss sits at the 666th level of the Abyss. A single sliver of the thing was able to empower the devil Asmodeus enough to slay his chief rival amongst the pantheon of good gods, and its theft was one of the root causes of the Blood War.
The Heart of Vecna is a minor artifact from Dungeons & Dragons that granted enhanced dark magical powers.
Hologram: The Judges Guild supplement Wilderlands of the Magic Realm had an artifact that projected a laser hologram of an elven princess.
Holy Water: Holy water is created when a follower of a benevolent deity infuses regular water with positive energy, and harms evil planar creatures and undead (including non-evil ones, though those are rare to begin with, because all undead are animated by negative energy). It's also used as part of the resurrection spell, and some people make use of club-like devices known as aspergilliums crafted to hold small quantities of holy water and release it at the press of a button. It also has an opposite in the form of unholy water, created when followers of evil gods infuse water with negative energy.
Legendary Weapon: The game has had many of these, from the Axe of the Dwarvish Lords and Sword of Kas in the 1st Edition Dungeons Master's Guide to the swords of the Forgotten Realms as described by Ed Greenwood (Adjatha, Albruin, Demonbane, etc.).
D&D is the Trope Codifier; its scrolls allow spellcasters to cast the contained spell once without using a spell slot, after which the writing on the scroll is erased and the scroll becomes magically inert. Unlike many later examples, the caster must still be able to cast spells of the proper type (arcane or divine); a Magically Inept Fighter can't use a scroll to cast fireballsnote Some editions have the Use Magic Device skill, which anyone can use, that can allow faking spellcasting ability long enough to use a scroll, wand, etc.. Also, many scrolls contain more than one spell (even the weakest can hold up to three).
In early editions of AD&D magic-users/wizards can only cast spells that they have prepared beforehand by expending a spell slot, not by reading them directly from their spellbooks. However, in the AD&D 1st Edition Unearthed Arcana supplement Gary Gygax changed the official rules to allow magic-users to read spells from their spellbooks as if they were scrolls in an emergency situation. Doing so destroys the spell in the spellbook (essentially "unlearning" the spell), has a 1% chance per spell level of destroying the two adjacent spells in the spellbook, and a 1% chance of destroying the whole spellbook.
Many magical items such as wands or rings have a limited number of "charges", some of which are consumed every time the spell within the item is cast. Once the charges are consumed the item becomes useless.
Lucky Rabbit's Foot: The supplement Book of Marvelous Magic has a magical Rabbit's Foot gave a +1 bonus to all saving throws. However, all herbivores seeing it took an instant dislike to the wearer (−2 reaction penalty).
In first edition, they qualified due to them only being able to be destroyed in a very specific manner. Even if you did damage them with conventional weapons, they were recalled to the immortal that created them. (Not sure what happens if the immortal no longer exists...)
In the second, it's either disenchantment by an uber-mage with great risk, or an unique method of destruction. Melted down in one specific volcano, crushed under the heel of one specific god, submerged in the tears of a hundred elven princesses and left to dissolve for the next 1001 years — that sort of thing.
Ditto with 3rd Edition Major Artifacts. At this point they say if you destroy one, you also attract the attention of whatever created it. They are probably not happy you destroyed their Magnum Opus. And are many levels higher than you if not a god. If you're lucky, they may be dead, but something powerful enough to create a major artifact tends to not just die...
Magic Cauldron: There are a number of magical cauldrons, including the Armor Bath (armors body parts immersed in the water), Ambrosia (produces a delicious wine), Archdruid (has powers of many other magical cauldrons), Blindness (any food placed in it causes blindness when eaten), of Creatures (allows owner to voluntarily shapeshift), of Doom (animates a corpse into a zombie), and Foretelling (allows the user to cast an extra Augury spell per day).
2nd Edition Tome of Magic: The Elemental Compass glows yellow when its owner is headed in the direction of a planar portal or planar boundary the owner is seeking.
The Arrow of Direction could be thrown in the air and commanded to point toward the nearest example of one of eight things: stairway (up/down), sloping passage (up/down), dungeon exit/entrance, cave, cavern. When it fell to the ground it would be pointing the correct way.
Al-Qadim setting spells
The Wind Compass spell allows the caster to know when he's facing in a particular compass direction (south, north by northwest, etc.).
The True Bearing spell allows the caster to know the direction in which a specific landmark or geographical site (city, town, significant land feature etc.) lies. It only works if the caster has been there before and the location is on the same plane of existence.
Many items have this sort of effect, such as the Gauntlets of Ghost-Fighting. These are when you want to kill incorporeal things but don't want to enchant all of your stuff. Even older are Gauntlets of Weaponry Arcane that make any weapon held count for purpose of immunities as silver and +1 to what it normally is.
There is also temporary version in spells like Magic Fang.
Magical Accessory: Many hundreds, if not thousands, spread out across the books. Popular ones are girdles and bracers of giant strength.
Miracle Food: Magic users in all editions of D&D have spells that can conjure food and water. Some magic items can do this as well, and most deities have it as one of their basic powers.
Mirror Morality Machine: The Mirror of Opposition, which creates an opposite alignment clone of you to do battle with. Helm of Opposite Alignment does it to the wearer.
Mithril: Spelled "mithral" to avoid potential lawsuits from the Tolkien estate. In 1st Edition, all +4 weapons and armor were supposedly made out of mithral-alloyed steel.
Moody Mount: The Obsidian Steed animates into one of these. If the rider is good-aligned, they must roll to control the beast or it goes to the Lower Planes and dumps them there.
Mundangerous: Marbles are mundane items that don't even cost a single gold piece, rolling on from The Complete Thief's Handbook. They are quite effective against anything with legs not noted for amazing agility. Instead of a saving throw (automatically going up as you level up), victims fall down, becoming vulnerable and losing time to get up, unless they made a Dexterity check (AD&D 2nd Edition) or a DC 15 balance check (D&D 3rd Edition; with balance being a skill most classes can't practically invest in) — and even if they make it they are "flatfooted" (as they are trying to balance) and can be hit by sneak attacks.
On a similar vein is soap. At a mere 5sp/lb, is one of the most useful mundane items. It's flammable (there's about a million ways to use fire), slippery (and so can be used much like marbles in any place that's damp), and you can clean with it. Always buy at least 10 pounds.
Naginatas Are Feminine: In Oriental Adventures (1985), the description of the naginata said it "is often the preferred weapon of women."
Precision-Guided Boomerang: A number of magical and mundane items. Specifically, melee weapons with the throwing and returning properties.
Purposely Overpowered: The Sword of Zariel, as mentioned above, is bonkers powerful, beating out even the Hand and Eye of Vecna in terms of power. The wielder becomes an angel in everything but name, gaining Celestial as a language, a massive boost to charisma, resistance to necrotic and radiant damage, wings, advantage on insight checks and Truesight. The sword itself, among other things, sheds light that weakens fiends around it and grants massive damage boosts, with no mechanical downsides aside from an alignment change and new personality. By the time the players get their hands on it, pretty much only the final boss remain, who's either an archdevil or demon lord. Even with the sword, the battle will be tough.
Rainbow Pimp Gear: Magic items generally aren't chosen because they fit well together aesthetically, but because they give powerful bonuses. Getting the best bonus combinations can fall into this.
First noted appearance is in module EX1 Dungeonland. A fountain's water turns into randomly determined potions. One of them is Hairiness: if drunk, the drinker's hair immediately grows longer and thicker.
It also appears in the 1st Edition supplement Unearthed Arcana. The Hairy cantrip caused a creature's hair to immediately grow 2-12 inches.
The Native American deity Heng has a bow that shoots lightning bolts that do 6-60 Hit Points of damage and have a range of 30 miles.
The deity Chih-Chiang Fyu-Ya has a magical bow that can hit any target within sight and causes any weapon thrown at him to return and hit its user. If anyone else attempts to use his bow the arrows from it will hit the user.
The deity Tou Mu has a magic bow that never misses a target within 100 yards.
Odin has a plus 3 bow that can fire 10 arrows per minute.
Ullers bow is plus 5. Arrows from it can hit any target he can see with no penalties for range and he automatically hits at a range of 200 yards or less.
Greyhawk campaign setting. The goddess Ehlonna has a bow that never misses its target even when fired at maximum range. Half of her arrows have a plus 3 bonus and the rest are Arrows of Slaying for various Evil woodland creatures.
Adventure C2 The Ghost Tower of Inverness. The Soul Gem is surrounded by an invisible force sphere which must be broken by the PCs if they want to retrieve it.
Scarab Power: Many artifacts, creatures or magic involve or are named after Scarabs. A few examples are the Scarab of Protection (a medallion that absorbs energy-draining attacks), the Golembane Scarab (a pin that allows the detection of Golems, and ignoring of their damage resistance) and the Scarab of Death (a cursed pin that will kill anyone holding it for more than one round).
Particularly notorious are the Hoard Scarabs. A hoard scarab is an eyeless, beetlelike creature that hides in piles of treasure. Thanks to its size and its silver or golden shell, it looks much like a coin when dormant (though close observation reveals its nature). A swarm resembles a pile of gold and silver pieces. If it bites a character, that character makes a reflex save. If the reflex save under 11 (14 if a swarm) it burrows into the character. When it's burrowed in a character that character takes 1d2 (2d4 for a swarm) points of Constitution damage per round. It stays inside until remove disease or heal is cast upon the afflicted character.
The Hammer of Thunderbolts. This is nominally a +3 weapon. But if the wielder is also wearing Gauntlets of Ogre Power and a Girdle of Giant Strength, it becomes +5, automatically kills any giant it hits, and (in early editions) was the only case in which the to-hit and damage bonuses from the Gauntlets and Girdle would stack together.
Silver Has Mystic Powers: Silver makes a good ingredient for so many magical items. There are also many creatures who take substantially reduced damage from any weapon that isn't silver.
Skeleton Key: Several exist in the game, including the Key of Opening, the Silver Key of Portals and Skeleton Keys (I and II).
Snake Charmer: The Complete Adventurer book has a magical item called "Flute of the Snake", which can be used both to control and summon snakes.
Stock Ninja Weaponry: The 1985 Oriental Adventures stats out a bunch of ninja weapons like shuriken.
Stuck Items: Cursed magical items in general are examples of these, as they will return to you and force you to use them even if they have been physically destroyed. It takes specific spells or combinations of spells to get rid of them.
Mirrors, garlic and holy symbols (and other holy relics) repel vampires.
Clerics can turn the undead, which causes them to retreat from the cleric.
The 1st Edition Advanced D&D supplement Deities and Demigods mentions that objects covered in dung are reputedly unable to be touched by the undead.
1st Edition Advanced D&D supplement Oriental Adventures. Magic items called "Noisome Spirit Chasers" are firecrackers that, when detonated, cause nearby spirits to leave the area.
Swordfish Sabre: Swordfishes can be used as swords. While they do have an irritating smell on land, they can be used with no penalty underwater.
Unholy Nuke: The Talisman of Ultimate Evil. In the hands of an Evil High Priest, it could be used to open a flaming crack at the feet of a Good priest and send him or her to the center of the planet.
Unique Items: In early editions, most magic items were generic and you could find any number of them.
Artifacts and relics were unique: only one of each of them existed in a game universe. Thus there could be only one Eye of Vecna, Codex of the Infinite Planes or Ring of Gaxx.
Some magic items of less power than artifacts and relics were also one of a kind. For example, in the Forgotten Realms there was only one Albruin (sword), Reptar's Wall (shield) and Mierest's Starlit Sphere.
In 1st Edition Unearthed Arcana with fighters and rangers, and in 2nd Edition with just fighters, a character could choose one type of weapon to specialize in. This cost one or more Proficiency slots, but allowed greater accuracy, extra damage, and even more attacks in a melee round.
In 1st Edition Unearthed Arcana, Cavaliers and Paladins got a "weapons of choice" at 3rd level, and another at 5th level. Attacks made with this weapon gain greater and greater accuracy bonuses as the cavalier/paladin gained in level, and (like fighter/ranger weapon specialization) allowed extra attacks per melee round.
3rd Edition has feats like "weapon focus" and "weapon specialization", which only work with one specific type of weapon.
In 4th Edition, many fighter powers offer a bonus when used with a particular weapon type, encouraging fighters to pick their powers based on their favored weapon type.
In Fifth Edition, this continues with "fighting styles" for Fighters, Paladins, and Rangers, granting bonuses with either ranged weapons, two-handed weapons, one-handed weapons with a free hand, shields or dual-wielding. Paladins, Rangers, and Fighters can only pick one of these styles, though the Fighter's Champion archetype can pick another style to make it two.
Zombify the Living: The 3.5 Edition supplement Sandstorm has the Dead Throne, an Artifact of Doom that brought the desert warlord Ten-Ap back from the dead and gave him the ability to turn the living into mummies.