Man, the list of where I
haven't would be a lot shorter. Of course, the ubiquitous bed and the very utilitarian shower. The shower makes cleanup a snap! (That should be the tag line for commercials about masturbating)
I've done it outside a great many times, also while driving, watching tv, porn on the computer, in a lake, sitting on the toilet at work, on a treadmill, in a changing room at a store. Man, now that I think about it I may have a problem.
I'm pretty sure I was busted by my college roommate once. We had a loft bed and slept feet to feet. I was wristing one out when he was sleeping (or so I thought). He suddenly sat up in bed. I stopped production and neither of us said a word.