I've been thinking for years though..theres nothing that really stands out for me. I really want to decide soon, so I can get on with work experience and have something to aim for.
You could also take the stamford test on ucas. They are quite amusing.
If you take a sciency course emolyers will be drawn to your analytical skills.
most popular at my 6th form were:
optometry (i was gunna take that...for the money)
i personally like
Earth and Planetry sciences
physics and astronomy