Probably laziness to the point they just sit on their bum all day watching tv, doesn't have a job or any ambition.
Someone who's left-wing with their political beliefs. If you've ever voted for Labour, then chances are we won't get on.
Hygiene is a big thing for me, if you stink or have bad breath or oily hair, I won't be attracted to you.
Music taste is also a deal breaker, if all you listen to is chart music then I can't imagine much conversation going on. I'd rather someone who's a real fan of music I don't like (metal) than someone who just listens to what ever is on MTV.
Also if you read the Guardian... just no.