Oof! - Used whenever I roll low on a Spot check, after a particularly unperceptive character who apparently needed glasses, because he always ran into stuff.
Feybag - A derogatory term used towards fey, elves, effeminate men, or anyone else we don't like.
Joeing the dice/pencils - Named after a player who always takes dice and pencils from other people, despite the fact that there are several in front of him.
The Mike G. Bonus - Higher ground bonus to attack rolls. Named after the player of a winged celestial character who always managed to get higher ground. Always.
Steveing the Dungeon - Named after the player of a character who could turn Incorporeal at will, allowing him to map out the entire place, traps, monsters, secret doors, etc. Now used whenever we cheat our way around obstacles.