[oldspowered67C10]

The air hammer w/ a chisel bit is the way to go. But you need a good one, I have a Matco one that works well but Ive used some cheap ones that were worthless.
The beauty of it is that while its smacking the hell out of the rivet to knock the head off it loosens it up and makes it alot easier to knock through once the head is removed.
Ive used the cutoff wheel/grinding wheel method before but sometimes even w/ both heads ground off the rivet still wont come out, especially if youre just trying to knock a rivet through rather than removing a rivet and the piece that the rivet is holding on.