Kingmaker problem

A common problem in games with more than two problems: You have a player who cannot win, but who can choose which of the other players will win. If he can't be a King, he can at least be the man who makes the King.

Examples include:

• Monopoly players offering their property for a song in a trade.
• Strategic games players going kamakazi on one player to aid another.
• Diplomacy, just Diplomacy.