I posted this highly contrived play on the NFHS forum, but it was near the bottom of a 100-post thread, so it didn't get much attention. I put it here for your amusement.
NFHS Rules
PLAY: 3/10 @ midfield. A27's legal forward pass crosses B's sideline in flight. B73, a substitute properly in his team box, is facing away from the field at the B40, jumping up and down to excite his teammates on the punt return unit. The ball strikes B73 in the back of his helmet while he's airborne, and rebounds over the field of play where (a) eligible A99 catches the pass in flight at the B35 and is downed there, or (b) safety B44 alertly grabs the ball in flight and takes it to the house. Ruling?