LEMMETWEETTHATFORYOU is probably the best Twitter forger yet.
Simply enter a username and it instantly generates their profile pic and background image.
Write your hilarious fake tweet and you're done.
For instance, I just forged the bombshell above about the new Angry Birds game.
Can you be as funny as I am? Doubtful. But I don't fault you for trying. I am one of the top two highest paid bloggers on Tosh.0.