Depends on the friend level (this goes for friends/bfs/etc). Sometimes something kooky that'll bring up a fun time together, sometimes a gift card to an electronics store, making them a good meal (no KFC or mac n cheese - unless it's part of the meal! lol), or taking them out to an arcade and playing for a couple hours (blow like $20-40 for both of you).
One friend of mine collects Darth Vader action figures like no other. So if I got him something super-rare that'd be one helluva gift.