Fivetuplets: Those weird breaks in "Pretty Noose" by Soundgarden. 1..+3... 1..+3... 1..+3... 1-2-3-4-5 1
Again, my counting looks better in my head than on my computer screen.
It's really not as hard as it seems, just focus on tapping your right hand on the beginning of the first beat, left on the beginning of the next, and then fit five notes in between as evenly as you can. I once managed to play fivetuplets with my hands while I played triplets with my feet.
Oh, and I remembered something about Zappa: the Black Page. A horribly complicated clusterfuck of triplets, fivetuplets, seventuplets, godknowswhatelsetuplets. Zappa would use it to scare the hell out of auditioning drummers, and then he set a melody to it. Legend has it Steve Vai sightread it. Or something.