I loved playing 21s as well at Uni. Also, played Fives. Description:
A simple drinking game that works really well as an ice-breaker or ‘palette cleanser’, if you will, between more complicated games. Players form a circle and each extend one clenched fist. During each round and on the caller’s command, every player chooses to either open or close their hand, therefore representing either ‘zero’ (closed) or ‘five’ (open). On their turn, each contestant is charged with preemptively guessing the total points in the ring (which, at the risk of stating the obvious, will always be a multiple of five). Anyone who guesses correctly is excused from the circle, eventually leaving one poor sod who has to down his entire beer as punishment.
Above description blatantly copied from game 6 from here: 12 Stag Drinking Games | Best Man's Best Man. Great game for getting everyone fired and competitive.
