Ultima Online

The first widespread commercial success in MMORPGs, first released in 1997. Developed based on Richard Garriot's Ultima series of games. Initially intended for each server to host roughly 300 players the game garnered unexpectedly huge numbers. Notable for its classless and level free skill based system whereby you could create a character with any combination of skills and gained power by using them. Instead of slaughtering monsters to raise your magic skill you used magic. Using a sword would raise your swordsmanship. Also notable was the game's emphasis on Sandbox gameplay. Little overarching storyline existed. Player freedom and enforcement of good behavior was expected. Unfortunately the developers didn't realize what they were in for. Approximately 1% of their total playerbase rampaged through the game world slaughtering other players by the thousands. They got around this by creating a mirror world called Trammel where PVP was heavily restricted.

Despite a rocky start the game flourished and is still running today. Several expansion packs have added content over the years to say nothing of drastic changes added by free patches.

This game provides examples of:
 * A Homeowner Is You - In the early years owning a house (or tower, or castle) was a large draw for the game.
 * Absurdly Spacious Sewer - the Britain sewers are a vast, roomy maze. They're also, essentially, a highway between Britain and the Lost Lands.
 * All in a Row - Tamers with their pets. Sometimes, with weaker pets, the AI is so poor that it seems more like an escort mission.
 * Ambidextrous Sprite - Not only are facing left/right mirrored, but when sitting down staves and the like bend where they simply bent the sprite rather than drawing new ones.
 * BFS - Quite a few examples, but the Soul-Seeker is probably the best. It's as long as the character, nastily curved, and looks utterly impractical - it is actually dangerous, which is nice.
 * Bizarre and Improbable Ballistics Heat seeker arrows, that can chase you forever.
 * Breakable Weapons - Everything breaks eventually except static objects. Every weapon comes with limited durability that gradually decreases the more you use it, and if don't remember to bring it to a blacksmith for repairs, it can fall apart in the middle of a fight.
 * Character Level - Averted, there are no levels at all.
 * City Guards - The guards are Nigh Invulnerable one-hit-kill teleporting Badasses. They come instantly when called by a player or NPC, and they'll kill any criminals within city limits, regardless of where the crime was committed.
 * During the original beta, they actually acted much more realistically -- they would have to be nearby to hear a plea for help and were strong but beatable. Griefers ruthlessly exploited this until Origin gave up trying to keep them even remotely fair.
 * Continuing Is Painful - Death is fairly punishing since you have to find someone to resurrect you and then go back to your corpse to get your stuff back. If you can't return within about fifteen minutes, your corpse goes through its final stage of decay, disappearing (along with anything you were carrying). If you were killed by another player, they have the option of looting any and all of the equipment left on your corpse. At least there's item insurance now...
 * Unknown if it is still the case, but other players weren't the only ones capable of looting a corpse. Many times, your body would be picked over by the enemy NPC who killed you, leading some monsters to become veritable pinatas if they lived near the entrance to a dungeon and could repeatedly catch players off guard.
 * Dronejam - Only in the pvp enabled side. You can push through one person/NPC with full stamina, but if you're 1 point under you can't. Though NPCs will move if asked, monsters are not so polite.
 * Dude, Where's My Respect? - Become a Lord or Lady, and you will be bowed to... but, good luck getting a discount. And, if you put a foot wrong, the guards will whack you like a peasant. A common peasant! Zounds!
 * Griefer - This game was legendary for how griefer-friendly it was in the old days, mainly due to the designers being unaware of the GIFT before they loosed the public on it. See also: The Great Player-Versus-Player Debate.
 * Horse of a Different Color - with the right amount of animal taming/lore, you can ride swamp dragons, ki-rin, bipedal dinosaur-like ostrich/lizards called ostards, nightmares, giant beetles, unicorns, fire steeds, and llamas. Some are literally rehued horse sprites, especially if you're using an outdated version of the game.
 * Katanas Are Just Better - Averted! You can get katanas (in medieval pseudo-England, yes...) but aside from having a good balance of damage and speed, they're a fairly average bladed weapon, compared to some of the others available. Like, say, an artifact halberd that can set things on fire.
 * Long Runner - Open since 1996 and still going despite all odds.
 * Lord British Postulate - Trope namer.
 * Made of Explodium - Purple potions, which used to chain explode for all your evil needs.
 * Metal Slime - A couple of examples, but the most irritating are the elite ninjas. (Yes, 1337 ninjas.) They appear suddenly, do considerable damage, zip around like nobody's business, and have stealthing powers, which makes them difficult to pin down and impossible to see coming. Also, they turn into cats, which causes great excitement.
 * Nerf - the trope namer.
 * Player Versus Player - A major problem early in the game, before the invention of the parallel world where all PVP is strictly consensual.
 * Poison Mushroom - The exploding toadstools.
 * Power Crystal - Used as a construction reagent, but doesn't actually benefit the player if used as an item. Other crystals contain imprisoned dogs and albino squirrels that will bond with the player and follow them around.
 * Power-Up - Alchemists can make potions with all sorts of exciting benefits. It's a shame that they only last for a few minutes; then the effect fades.
 * Purely Aesthetic Gender - A player can play as a male or a female. The only difference this will make is that only female characters can wear certain types of armor, and some articles of clothing become more... shapely on females. (Note: dresses are made to look shapely on any character. This leads to crossdressing male characters... sporting impressive breasts and hips.)
 * Shoot the Medic First - No player party can expect to survive for long against a powerful monster without a cross-healer. In PVP, it's greatly recommended to take out anybody who looks like a wizard. Which is, in a world where magical items have properties that make them useful to melee fighters as well... everybody.
 * Strong Flesh, Weak Steel - It's easier to hack up a golem, which is made of steel, than a well-trained human character in leather armor.
 * Suicidal Overconfidence - The fairly new Paladin skill of Chivalry is almost game-breaking in its usefulness... but, of course, there are always those who will become complacent. Unfortunately, because such players have rarely had to develop their running-away skills, they're not very good at escaping. Monsters tend to be lured straight back onto the rest of the party, which they make mince-meat out of, as the dead Paladin is typically the strongest defensive member. Leeroy Jenkins lives!
 * Tele Frag - The game prevents teleporters from splinching themselves with others, as it's impossible to teleport to a spot that's blocked. Heavens help you, however, if you teleport unprepared into the midst of a spawn... or an enemy guild.
 * Thigh-High Boots: Standard footwear around these parts.
 * Trope Maker - UO was the first widely-popular MMORPG (Meridian59 came earlier, but very few people ever heard of it), and made a lot of the MMORPG tropes we see today.
 * Unbuilt Trope: Ultima Online actually has more in common with EVE Online than EverQuest or World of Warcraft. It was Everquest's content-based model, instead of UO's Wide Open Sandbox, that became dominant in the MMORPG world.
 * Video Game Cruelty Potential - Being evil to both monsters and other players for fun and profit for 14 years.
 * Warp Whistle - "Kal ort por!"
 * Wide Open Sandbox
 * Wizard Needs Food Badly - Sort of subverted. There is a hunger stat, and characters go from extremely hungry to being so full that they can't eat any more--- but it doesn't seem to have any effect on gameplay. Not that some members of the playerbase will ever believe that.
 * You All Look Familiar - Apart from skin colour, hair colour, hairstyle and clothing, every character has the same face as others of their species. As there are only two species - humans and elves - this gets a little limiting.