the beef balls at the stall near my house. i swear they can bounce off walls and ceilings.
/me hides from flames
ok ok serious now... i've used a variety of bounce devices in my quest to achieve the best softening effect, including the Sto-fen Omni bounce, Lumiquest pocket bouncers, home-made bounce cards and they all suit different lighting situations.
for example, if it's a outdoor event or indoor with very high ceilings (like a church wedding), i'd opt for the Lumiquest (no need to bounce off ceilings), but if it's indoors with low ceiling, the Omni-bounce gives good coverage.
my current fave now is a plastic Metz bounce card (i adapted it to fit my SB-28/80DX). what i like about it is i can use it to shoot portraits as well (a bit hard to explain - bend the flash head 90 degrees to the right and stick the bounce to the side of it).