Our drummer from our old band had a music store. We used to piece together old bass and guitar parts and make "barely useable" instruments. We'd play them on the last song and then smash them. People loved it and always fought over the parts. It was also extremely satisfying. As long as we cleaned it up the soundguy/club never cared. In fact, we usually asked permission before going on and no one ever denied us.
Old, usually broken but easily fixed, guitars and basses are always on craigslist for next to nothing, as is First Act/Esteban stuff that's dirt cheap. You can also go to mom-and-pop music stores and get something that's broken from their back room for super cheap and fix it so that it will last you one song.
So why is it that no one smashes equipment anymore? Not even bigger bands do. I think Nirvana were the last mainstream band to regularly smash stuff, and I NEVER see local bands do it, ever.
Anyone else do it? I've got an old Memphis in the basement with a cracked neck that's just itching for it...