My experience: Had a long-term gf that I discovered had been cheating on me for several months and decided, as a petty form of revenge, to give her some unknown going away creampies. So for a couple months, every time we had sex, I came inside her without any indication/warning (she was on top and thought I was pulling out and shooting on my stomach). She made several comments about being wetter than normal after wards but never caught on. It turned me on so much at the time and was some of the hottest sex I've had. We are obviously no longer together and she still doesn't know about it. Just curious if anyone else had ever done anything similar, not necessarily for the same reasons obviously.