My wife loves to have me stand beside the bed naked so that her Bull can see my tiny little penis and humiliate me while he takes and enjoys my wife in front of me. If I get hard or cum while watching it is even more of a turn on for them.
I absolutely used to love watching my wife getting fucked by the guy I was standing there naked and jerking off and it wouldn't take me long to come at all. And sometimes I'd actually shoot my cum on them