Boss OD-3 (Bass Overdrive)
This thing is too sterile. I don't like active anything in re: to distortion, especially not eq. Too much nit-picky tinkering with the waveform is always going to make it bland. Give me a solid analog circuit any day. Germanium, baby!
Boss OD-1 (old school gray overdrive)
This pedal gets the tone in the ballpark, it sucks a bit of low end, but pleases with a nice smooth creamy overdrive. I like it if I want subtle grind. Nice mid presence.
Ibanez Phathed PD7 (?)
I unfortunately couldn't, in any setting, get the mild overdrive they claimed it could produce. This is a total Korn pedal. Not to say that's bad, but not what's advertised.
Ibanez Tubescreamer
This is my fave, with the addition of Big Muff. I have a custom built Tubescreamer clone that has a second gain stage and twin low-pass filters...gets the tone with a tad more natural bottom end. Kick in the second gain stage, and look out!
Big Muff Pi
Classic pedal for real-deal fuzzbass. Sure it kills alot of low end, but sometimes you really want that to buzz thru a mix.
From quasi-subtle to full on buzzsaw, a great standalone pedal.
Boss Heavy Metal
The gain on this is so sick, when you send bass thru it, it has a tendency to get a real nice squish-compression that just makes the tone so thick and smoov, it's unreal. Not good for blowing thru the mix, but in the right setting, with cleaner guitars and whatnot, it settles in really nice.
ZVex Wooly Mammoth
This pedal is insane. Not subtle to the least, but the tone is Godlike. For great in your face distortion with *good* amounts of shaping AND low end, get this pedal. It's pricey, but a tad one-trick-pony...
Fulltone Bassdrive
A really nice smooth overdrive, mimics a tube gain stage nicely, but a tad distorto than overdrive...very useful and not annoyingly buzzsaw-like
Royal Octavefuzz
Vintage pedal my pops picked up at a flea market... good basic fuzz that doesn't track well at all on bass...but i like the way it burps.
MXR Bass DI+
More preamp than fuzzbox, it still gets a nice overdrive, much better than the o.d. coming out of a SansAmp BassDriver, which is annoingly squarewave, like a ProCo Rat.
There are others, but that's a taste...