I've used distortion on occasion, but never really relied too heavily on effects for bass.
8-string thru OD- yikes. BIG sound. Tasty.
I've got a Roland V-bass that's pretty fun to goof around with, but unless you're doing a bass-centric project it seems like most fx are overkill.

I think Tony uses an octave divider for a few AM songs, it gives a nice 8-string kind of tone, and he likes some distortion or overdrive now and then, but that's about it. Live, anyway.
We try to keep an 'anything goes' kind of attitude in the studio.