I always think bassists have to scrabble around in the wake of guitarists to find pedals that they know will work with bass. This is changing, but it seems that until fairly recently the prospects were bleak for bassists. Anyway, what pedals did you find worked with bass, even when you didn't see it coming? The battered DOD pedal with the battery cover missing, languishing in the back of the practice space? The drunken Ebay purchase that took four weeks to come from China? The piece of vintage gear you had written off for the last ten years until you dusted it down? To get the ball rolling... mine is the Boss OD-20. Boss killed this one off quickly. Guitarists hated it. Some of the settings (the Rockman emulator especially) make no sense. Like other digital distortions it is somehow harsh AND muddy at the same time. Swampy, slushy, turgid and ugly. However, one or two sounds shine with bass. Notably, the Tubescreamer and Klon (lol) sound good and retain the low end perfectly. Yesterday I dragged it along to my ampless band's rehearsal (Roland V drums and pedals into a mixer into a decent stereo PA system). The line-out has a cab sim attached and it sounds really good! The "Bottom" control is in fact a sub-octave synth that tracks really well until the 12th fret on the G string. I was surprised, and will probably take this (over the usual barrage of drive, fuzz and compressor pedals). It looks like a kids toy, but it sounds pretty decent on one or two settings.