Rain
Some people are hoping for rain, to make the race more exciting/unpredictable. I can't see why we need rain any more. In years gone by, F1 was a procession, with little overtaking (Hamilton, excepted). In 2011, overtaking is no longer a problem and there is now plenty of excitement during the race, without needing rain to add to the unpredictability. Every race is now difficult to predict until the chequered flag has fallen, so I really can't see any point to have a wet track.
I want rain because they disable DRS then.