How do I take these off! (cranks)

i've removed them with a hammer a couple of times.
loosen the nut, but don't remove it, leave it just on the end of the bolt to stop it mushrooming over.
try and use as few hits as possible. the more hits you take the less likely it is to come out. 1 or 2 should do it.
(i think this is pretty much what sheldon suggests)