gamer's high
The subtle, or intense, feeling of pleasure or euphoria experienced by some who are way too into playing a computer or video game. May happen during extreme late night gaming sessions, while getting a bigger score or pwning more noobs that you ever have before, finally beginning to beat that boss/level, or even in anticipation before you have even started playing the game.
"Counter Strike is like a drug. I get gamer's high even before I fire it up."
Gamers High
The feeling of increased awareness when playing an intense mission/online match on a video game. Also see gamers twitch.
Joe had his eyes wide open and (somehow) fully awake at 3 am playing Black Ops, stricken by gamers high.