Rules Lawyer
"Rules lawyers are a common breed of gamer that basically exist to make sure that every single game you ever wanted to play takes four times as long. You want to just take the hit, make your fortitude save, and move on? Too bad, the rules lawyer is arguing with the DM about how many people can physically fit in a single five-foot-square, just so his character doesn't have to take d6 damage from the poison arrow trap. You want to assault your opponent's leaping Hormagaunts with your Fire Warriors? Well boo for you, you moved that one model too far during the movement phase; you need to move it back until it conveniently no longer has charge range. The rules lawyer is a vampire, sucking all the fun out of the game, and the sooner you drive a stake through his withered husk, decapitate and bury his body, and never speak of him again, the happier everyone will be."
- - Faggot McStoner after the 11th time he has been called out for not knowing the rules to the game the group is playing
- A wargamer speaks
Rules Lawyers are there to ensure everyone is actually playing the game properly and not inadvertently cheating. In competitive games this is more important than cooperative games. In a game of 40k letting a unit arbitrarily make an assault when it is not entitled to is cheating and makes any victory that results in it invalid and anyone who takes pleasure from it a massive bitch.
- A roleplayer speaks
Rules lawyers are usually That Guy at the table, who is gonna get butthurt when you handwave a mechanic that is essential to their min/max munchkin build. They truly believe that Rule Zero is a blasphemy, and can't act in-character for shit. They'd rather roll Diplomacy checks than negotiate with an NPC at the table.