Since we've had these for basically every other instrument, we should one for the bass.
I am fully aware that this is going to turn into a Les Claypool thread, but who cares?

John Myung (Dream Theater, Platypus, Jelly Jam)

Geddy friggin' Lee (Rush)

Steve DiGiorgio (Death, Iced Earth, Testament, Sadus, among others)
Come on, he uses a fucking fretless bass and still tears it up.

Stu Hamm (Steve Vai, Joe Satriani, Solo)

Steve Harris (Iron Maiden)

Tony Levin (too many to name, most notably King Crimson, Yes and Liquid Tension Experiment)

John Paul Jones (Led Zeppelin)
Couldn't find a good picture of him with a bass.

Lemmy Kilmister (Hawkwind, Motorhead)

Roger Waters (Pink Floyd, solo)

Billy Sheehan (Steve Vai, David Lee Roth)

John Entwistle (RIP) (The Who)
And of course,

Les Claypool (Primus, and I don't feel like listing all the others cuz their titles are really long)
And that's all I can think of right now.