For me the most exciting thing is when I watching my wife with another man, and he cums inside her. Even though she is on contraceptives, it is still very hot story. My wife read in one forum that this is a fantasy of sperm competition or something like that.
I love watching the bull's cock halfway in her pussy and starting to pulsate as he cums inside. Then he slowly takes out his cock and white sperm begins to flow out of the pussy. Realizing that he just came inside my wife, and she might get pregnant, I get very excited.
I have no fantasy that she would become pregnant from another man, and we are trying to be as safe as possible in this matter. But some deep feeling inside me rejoices as I watching my wife with another man plant his seed in my wife.