A few games that are made to be unfair to help demonstrate that life really isn't fair
Football - one goalie can use hands, other can't.
Any team game - uneven numbers
Dodge ball - one team is out if they're hit below the waist, other if below the knee.
Basketball - one team can move with the ball (like basketball), other team can't (like netball)
A twist on this is to just say there are no rules whatsoever - anything goes - and watch the destruction. Helps demonstrate that rules in life are usually for the best.