if you're looking for really thick, i have two that we're on my pedalboard for all my live shows. the discontinued earthquaker devices crimson overdrive, and the DOD/Black Arts Toneworks Boneshaker.
the EQD is a germanium diode overdrive based off of the old Dallas Rangemaster. It gives you a ton of texture on a bass. Absolutely massive sludge and crust tones paired with my sansamp, still articulate enough for triplets and speed picked riffs, plenty of sustain.
the Boneshaker was a little harder to tame, but it's meant to be fiddled with extensively to sit well in a mix. I'm too dumb for a pedal with six EQ knobs, but when i could get it dialed it sounded awesome.
there's so many good suggestions in this thread, I really want to try all of them now.