When two male competitors attempt to prove they have a bigger penis and testicles than the other. This is done by dipping the aforementioned area in a full pint then removing the genitalia from the pint. The two pints are then compared to see whose is the fullest. The person with the fullest pint loses the wang off, this is of course displacement in its most beautiful form.
Two blokes at a club/pub/party called "Mr. Ratty" and "Mr. Badger" decide to challenge each other to a wang off over a row about a girl. The winner claims his prize.