Geeks, anything geeky!
Nothing better than a guy dressed in a nice black suit, with black shirt and tie, trying desperately hard not to draw any attention to himself, hiding behind his monitor, typing away at some really in depth PHP or some such... Knowing full well that behind his Komodo Edit window he's reading up on Martok's family history on Memory Alpha, and under that black shirt you just know he's sporting one of Sheldons memorable t-shirts!!
The only thing that competes with that is female geeks, though generally missing the all black attire, those dark rimmed glasses and blend into the background outfits really do it for me!