Naked iguana wrestling
The two combatants strip naked. A belt (or equivalent) is placed behinds the two competitors necks when facing each other on all fours. On 3, the wrestlers (when bound) attempt to back away from each other (as iguana do) and the first to cross the starting line (the original midpoint of the two) loses.
Shit got weird last night and I ended up naked iguana wrestling my mate.