One thing I cannot stand to see is a cluttered dashboard. Frankly, I find it disgusting and it shows an obvious lack of care for your vehicle. Not only is it gross, but it's also dangerous. In my eyes, there's no excuse to let papers, trash, and god knows what else pile up on your dashboard. Clean that shit up.
Two other things I despise are bald tires and low tire pressure. Both equally dangerous and something that most people (who aren't car people) don't pay much attention to.
So, what's your biggest automotive pet peeve?