A pirate of Silicon Valley
There are exactly two figures in the upper echelon of Silicon Valley corporate life who would be recognizable to the layman: Steve Jobs and Bill Gates. Of the two, Jobs is by far the easier to lampoon, with his weirdly consistent uniform (black turtleneck and jeans) and unsettling intensity. Gates, who these days looks more or less like a typical wealthy middle-aged guy, is best captured in his youthful days; the fellow above, with the bad haircut, aviator glasses, and smug smile, does a fine job of it.
If you're attending a gathering of more tech-minded people, you could go a bit more obscure -- grow a beard and a scowl to do Larry Ellison, for instance, or Harry Potter glasses and a grin to emulate Linus Torvalds. If you can bellow and perspire on cue, you might want to attempt Steve Ballmer, but under no circumstances should you do so if children will be present.