For Octave down I love my OC-2, it's well documented!
Or similar tones, but without the -2 octave (which not many people use), check out the DOD Octoplus.
If you want up and down, POG is a decent bet, the Earthquaker Devices Organizer is cool, with some cool quirks. If you can find one, the Pearl Octaver is well loved.
So many to choose from, have fun going through them and trying all, then move on what you don't like. It's the ongoing quest
Si