speed running is beating a video game as fast as you can. apparently these guys record themselves and post their leet speed running skillz online for all to worship. http://speeddemosarchive.com/GameList.html
http://bisqwit.iki.fi/nesvideos/ Tool assisted runs are more fun to watch though they require very different skills (they don't require reflexes, for example, but they require a LOT of precision and patience).
Guys who played Marathon used to do that, they'd run through a level, firing no shots, and taking no hits. You could get right past the enemies and complete the level without them having time to get you. Weird. /jzero