Con

con, Con, n. 1. a gaming convention; examples include [] in Geneva, Wisconsin, [] in Atlanta, Georgia and [Game Fair] in Columbus, Ohio. [GJ1]
2. short for Constitution, a common stat in RPGs. [EDE]
3. (MUD/Everquest) short for "Consider," a command that allows you to figure out if you can actually take a particular mob or player character in one-on-one combat. [ME]
----
Addendum (meaning #1): Usually held at a hotel or convention center over a holiday weekend, cons feature tournament games, free gaming rooms, dealers rooms, exhibitions, video gaming rooms, lectures and panels, costume contests, LARPS, movie and video screenings, and art exhibitions. Activity is often around-the clock. [GJ1]
Addendum (meaning #1): Cons are rife with caffeine abuse. My friends and I went to OrcCon in L.A. one year without a hotel reservation. We figured since we'd packed in 6 bottles of Vivarin, 4 cases each of Hershey bars and Mountain Dew, plus a industrial size jar of atomic fireballs (jawbreakers), we weren't going to sleep anyway (we didn't from Friday at 20:00 to Tuesday afternoon at 15:00). [GF]
Addendum (meaning #2): Unlike some stat abbreviations, "con" is a word unto itself, interchangeable with "constitution."
Ex: "What's your character's con? I need to know to see how badly you've been killed."
Addendum (meaning #3): On EverQuest, usually used with a color: light green, green, blue, black, yellow, or red, reporting the color of the response text given to the player -- light green is easiest, red is most difficult.
Ex: I was going to attack the froglok but he cons red, so I'm going to get a group together to kill it. [EDE]