A really nifty one from Runoff Groove. They added an input and output section to the Bazz Fuss to give it a ton of output (HOLY CRAP LOUD) and put in a big muff tone stack. Sounds remarkably like a big muff. And it's loud.
Did I mention that it has lots of output? Unity on the volume knob is somewhere right around ... off.
Oh, and it's loud. About 40db of volume boost.
Seriously, it was hard to do this demo. I have neighbors around and want to keep my ears, so I never turned my guitar up all the way and left the volume at 10:00.