Clickystick: Cure Light Wounds wand. I'm not sure of the derivation. I've also heard pixie stick (from the candy), but not happystick.
Buff/Nerf/Tank/Meat Shield/etc.: The usually MMORPG/tabletop crossover terms are all in effect.
"Whatever you say, Gary": Said to a GM who has just killed a PC. Named after a previous GM in the group (one of my favorites, actually) who was known for running extremely lethal campaigns.
Elevator: Any really bad idea or dangerous location. Commemorating a session of Champions in which the superheroic PCs managed to score a TPK without ever interacting with a villain or, indeed, any NPCs at all; an elevator and Champions' lethal falling damage were key to the event.
"You Magnificent Bastard, I read Your Book": An exclamation used whenever a player or GM does something particularly dastardly or which screws over another player. From a line in the movie Patton (Patton says it after defeating Rommel's forces in North Africa), although its usage is actually the opposite of the original phrase's. Sometimes shortened to one half of the phrase or the other.
Temp: A PC whose player doesn't want to stick around for the campaign; killed off or abandoned by the end of the session. Slang for 'temporary worker.'
Dungeon Fever: What PCs contract when their players can't make a session. A virulent, incurable, chronic disease, often afflicting as much as half the party. Some tragic PCs have been incapacitated for months at a time; others appear to have died from the condition (the player either brought in a new character closer to the party's level, or the campaign ended before the player returned).
"I find the ground": Rolling a 1 on a Spot or Search check.
Pulling a Sterling: A PC's creative and accidental suicide. Named for a player whose PC, when told to 'drop the alchemist's fire,' did so - all twelve vials he was wearing on his belt. The other characters declined to raise him.
"I reach into my coat for a potion": Another term for a PC's creative and accidental suicide. The last words ever spoken by a PC (well, his player's last words with that character, anyway) who, after having survived domination by a psionic dragon (only by rolling a natural 20), the explosion of his own stash of explosives, a massive battle against dozens of enemy soldiers and capture by the enemy leader (who had a grudge against him) - only to die while parachuting from an airship because he announced the quoted action while a dozen elite troopers on the ground were under orders to shoot him if he did anything suspicious. Reaching into his coat (him being famously laden with grenades) qualified.