Unfortunately, my favorite ass pic (that's relatively sfw) doesn't fit into a signature, and is ruined by shrinking it :(
I've wanted to do something w/ this for at least a year now, it just never works right.
(click for the full glory)
Artist's name is sawasawa on danbooru if you're interested in the rest of his stuff. There's an ass ton (pun intended). I'd give my left arm to be able to draw like that.