A sped up high-five where two people put their arms as far back as they can spin them and then they sling their arm around as fast as possible and slap the other persons hand. Usually done between two best friends.
Like the trust fall, but a guy (or girl) raises their leg up to a 90 degree angle and then a guy places his genitals on the persons leg, trusting that they will not kick their knee up and hitting their genitals.
Boy 1: Leg Trust!
Boy 2: No way, you just want to fell my balls rub your leg.