U2--I think it was leaked, but I honestly can't remember for sure.
Yup, it definatly was, the E3 demo from almost a year before it was released (man, those E3 demos are leak magnets!). Also I think I remember a few other games were leaked, but I can't remember which ones. Man, they really need better security on these things, you would expect companies like Valve and ID and Epic to have the most security on their games.
Oh, and I think the full version of Yuri's Revenge was leaked like a month before the game was released.