I don't like touching doors with my bare hands
In the men's rooms at my workplace, I always use a paper towel when touching the doorknob to leave. There's even a big garbage can next to the door in which to toss stuff as you leave, so I see I'm not the only one. Has to do with the fact that some of my co-workers don't wash their hands after taking a shit.
I don't mind touching other public doorknobs, but to compensate I've got a supply of sanitary hand-wipes in my car. I'll have one in hand when entering a restaurant, wipe my hands after going in the door, and then toss it in a garbage can before placing my order.
Yes, I've got the OCD hand-washing thing. Not as bad as some people, but I do have to keep hand lotion around so they don't dry out too much from all the washing.