In my college days I dated a wonderful woman who liked keeping things a bit edgy. She invited me to meet her parents for dinner at their home. Her parents were seated opposite each other and she sat directly across from me. She daringly lifted her foot and started massaging my crotch with her socked foot, distracting me and getting me hard in no time. She then asked me to get her more water, knowing I was tenting. Much to my relief her mother got up and refilled her glass!
None of this was done as a dare but it sure would make a good one.