sub drop with choir, for sure!
run a sine sweep through it, see how the frequency response is with the choir functions and stuff like that.
try to route effects in stupid orders, like distort or mess up the signal in front of an effect that needs tracking, like the choir function. run reverbs and delays in front of the choir effects (or harmonizers or whatever the hell is on that thing). there´s always something that could mess up :P
try to find buttons that do very different things, like they have conflicting functions. then, go insane pushing those buttons real fast, trying to make them counter each other so it loses it. i have no clue about the unit though, so this might not apply at all :P