At an end-of-the-season skills competition, we've done a few interesting side games:
(1) Speed Golf: Doesn't matter how many strokes it takes you to put the disc in the basket, but the winner is whoever completes the hole(s) in the shortest amount of time possible. Hilarious watching people sprint after their disc while it's still in the air.
(2) Knockout: Variation of the basketball shoot-around game. Players line up at about 30-40 feet from the basket with their putter. Player 1 will shoot and Player 2 shoots just afterwards. Player 2 is trying to sink his putt before Player 1. If he does so, Player 1 is "knocked out" from further competition, single elimination style. The next player in line may not throw his putt until a successful putt is retrieved from the basket.
(3) Opposite-Hand Long Drive: No rollers or thumbers. Spot the disc from where it lands. Define a fairway with rope and watch everybody try to rip their disc with their non-dominant hand.
We've also done rotational putting stations where you putt 5 times from each station. 2 points for a make, 1 point for chain-out, and bonus points if you make all 5. We had one station that was a longer putt from a raised pad worth double points (4 points for a make, 2 points for chain-out).