I gave someone head on the roof of their apartment building once, in full view of the building courtyard (where the nazi apartment manager or any of the tenants could have seen us) and about a 3 street radius. We would have screwed on the roof, but the shingles were too rough on my ass.
When I was still in the military my wife (then girlfriend) came to visit me. I was taking her back to the airport and we had some time before she had to catch her flight. I had a little Honda Del Sol at the time so sex in it was impossible. Any way we pulled in to this construction site and proceeded to have sex on the hood of the car. When we finished we realized that there was a bunch of construction workers on the top the hill about 100yards away. It was 6PM on Sunday we had no idea they were there till we heard the clapping when we finished.
we've been pretty adventurous with threesomes, etc.....done it at the lake in the water with people around, my next big thing is to get to do it in a dressing room, or maybe a restroom at a club, or even a club, but i'm a chickenshit!