Fugly bus - The mysterious bus that whisks away all the ugly people from the bar and replaces them with their beautiful cousins while you’re in the bathroom draining your tenth pint.
Jack and Jill - A shot of Jack Daniels and a beer.
Jumping on the grenade - When two groups of the opposite sex meet, one member “jumps on the grenade” by talking to (or possibly sleeping with) the least attractive member of the other group so as to ensure the success of the rest of the group.
Keg commander - The boisterous chap who hovers around the keg so as to ensure everyone knows how to properly pour a beer.
Riding a rocking horse into battle - Getting drunk on 3.2% beer. (Silly Oklahoma beer laws often lead to this, since any beer stronger than 3.2% has to be purchased in the liquor store)
Not that I've actually participated in such activities, mind you...
Great list, book-marking.
I always let my buddies be the "grenade jumper". I never returned the favor either!