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.