(noun) a keg-buyer is a person who, when asked to leave an overcrowded party, offers to "buy" the keg in exchange for being allowed to stay.
"Keg-buyer" can also be used to describe any person who is attempts to use money to win friends or exhibits other whack behavior.
(KB is an acceptable abbreviation for keg-buyer)
"Dude I told this little maggot kid to leave the party and he offered me $20 if I let him stay! Fucking keg-buyer."
"Wow, you're seriously talking about how much money your Dad makes--stop being such a keg-buyer."
"We call the keg-buyer 'KB' on the sneak so he won't know that we're talking about him."