Let's see,
in a new sub-division that was being built, in the back of the car and completely naked. I was 18 and she was 17, but the cops didn't ask for her ID.
Same GF, in her bedroom eating her for I don't know how long, and her mother comes home unexpectedly. The smell was so strong in the room that there was no denying what we were doing and she was furious.
Caught by the maid at a hotel during a lazy morning because we forgot to put the "do not disturb" sign on the door. Especially shocking for the maid because I was 24 and my partner was 46.
Caught by cops with the same woman necking in a park after dusk. Their reaction was pretty amusing at least.
Caught by my own mother while having sex in my room with a gf. We were under the covers in a spoon position with the tv on when my mom walks in to "check" on us. We chatted about the show we were watching with me lying there with my dick inside my gf. After my mom left, we just picked up where we left off. Mom's so clueless that I really think she didn't twig to what was going on.
Same gf, now the first wife. We're driving thru a quiet suburb at 2am with her completely naked in the front seat while I play with her. We accidentaly drove past a group of kids walking down the shoulder. Our first clue was a kid shouting "Holy shit! Look at that!" LOL.
Man, a lot of times when you list it, but it could have been a lot more. There were certainly plenty of opportunities.