The phantom
People join the game, and One player is randomly chosen as: THe phantom, only they know they are the phantom, no one else does.  The phantom gets lots of minerals and gas, a little at the start (like, 10 minerals and gas per sec) till a LOT near the end (like, 100 minerals and gas per sec, maybe more)the phantom's goal is to kill everyone else, or trick everyone else into killing each other, as the phantom, you don;t want people to know that you are the phantom, until it's too late.  The goal of the nn-phantoms is to kill the phantom.  When the phantom dies, the other players win, but if the phantom kills the other players, the phantom wins. 

One time it was 3 players, we didn't know who was the phantom, I wasn't it, but I had  a sneaking suspicion on who was the phantom (the trick was, they made medics with no vespine geysers, and you need gas to make medics so the must be getting gas from elsewhere, so they must have been the phantom) They were massing marines, but they had very few buildings to make things with, so, I, who had bases all over and was mining like crazy, made about 65 wraiths, cloaked them, and rushed at his base, i destroyed his starport so he couldn't make sciencee vessels, killed his command centers, then his barrackses, and was about to win when, I was drophacked.  SInce then, I have never played without an Anti-Drophack.