Well... something geared towards him and his likes...
I don't know him or what he likes, so cant suggest specifics...
But my guyfriendwhoImcrushingonwhoisalso25 likes penguins. So I got him a penguin shirt and fuzumi (handknitted stuffed animal Fuzumies! ) for his birthday.... Usually I don't like to get something when its someones interests... like friend likes cats, so EVERYONE gives her something catlike, which gets tiring after a while... but he *REALLY* likes penguins... to the point he gets happy when he sees his penguin mug and stuff... so knew he'd enjoy it~
Of course... stuffed animals aren't exactly "guy"-like and stuff... but he's got a goomba on his desk at work, and I like them and mess around with him, so got him something thats reminiscient of me... He likes them :3
Also got him a giant penguin poster <.<;;; Giant penguin poster! Also zazzle.com, so clickies!
For no reason at all... which he reallllly liked since he was decorating his new apartment...
So really... anything he can use/enjoy... I get a lot of goofy things that a lot of ppl wouldn't stereotypically give a guy, but they enjoy them anyways *shrug*
Books as well... like a recommended series and stuff... dunno theres tons of things out there
But if he's geeky, might wanna check out thinkgeek.com (zazzle.com mentioned earlier, has a ton of posters, shirts, and random things postcards, mugs, shoes, bags, etc... a TON of different designs O_O;; can spend days looking at things haha)