I like this topic... if for noting else, everyone is being pleasant and not fighting.
For me, most daring might be on top of a beach side tiki-bar after the place had closed, during a college spring break trip. The bar was wide open to the nearby beach where dozens of couples walked by clueless of the two naked people going at it on top of a bar that was crowded with people doing shots just a couple hours before.
The most fun (and something I want to do again) might be the time I did it in a dressing room at a clothing store in the mall. She tried on clothes as I watched, and then we had some fun (but silent) sex. It just enhanced the fun knowing we were up to something slightly naughty with all the oblivious shoppers nearby. Any ladies up for a shopping trip?