Les Claypool's sound on the [i]Tales from the punchbowl[/i] album is a (to me) a superb sound.
Also the usual suspects regarding gnarly, gritty low end: Bruce Foxton, Geddy Lee, Justin Chancellor
Spent quite a while finding a sound that emulates these chaps, but also works with my playing style (really aggressive right hand with floating thumb). Turns out it's a Jazz bass.