I definitely agree with people on the smoking one. The smell is terrible, and even if they don't do it around you, you can often times smell it on someone.
Arrogance is also a huge one. This applies to anything in general. I find arrogance to be very obnoxious.
Lying is another huge one. I hate being around people who frequently lie, whether they think they're protecting me or making stupid claims, both make me rather angry.
Excessive use of deodorant or some kind of scented spray. Biggest one I seem to run into are guys who cover themselves in Axe and reek of a cleanser-like odor that burns your nose.
Insecurity or general lack of confidence in oneself. I do not enjoy babysitting people while they sit around moping regularly and avoiding everything. Granted, everyone has their moments, which I'm ok with, but if it becomes a regular occurrence, I'm gone.
Lack of proper hygiene. Greasy hair, bad breath and sweaty odor in particular tend to be a turn off.
Excessive ghetto attitude or style. A mild accent is ok, but when it gets into the territory of making someone sound unintelligent, their pants are hanging halfway down their ass, or they have 'bling' jewelry on, chances are I don't want to be around them. Also, that weird walk where some guys will hunch their shoulder over a bit and hold their hand in front of their crotch while walking looks really dumb, no idea what the hell it's called.
Excessive Patriotism. This partly ties into arrogance, as a lot of overly-patriotic people tend to be really arrogant about it.
Excessive Religious Dedication I'm ok with laid back religious people, but if I have to listen to speeches on a regular basis or they want me to attend church of some kind, I'll pass.
I also won't date someone who opposes various human rights and feels that it's necessary for them to govern how other people live their lives. An example would be those who try to prevent gay marriage and various other freedoms which don't hurt or effect anyone else.
I also find people who go on crusades about drugs and such to be irritating. I'm not particularly fond of them and I don't use them myself, but it's still really annoying to hear fanatical rants about it.
People who refuse to drink at all, or drink excessively. Drinking is fun sometimes and I don't want to be lectured for getting drunk on occasion or be around someone who refuses to join in. However, the opposite is also bad and extremely unhealthy.
I know there's some others, but I'm running out of ideas offhand.