People that don't wash their hands after being in the public restroom. Come on, we're all professionals here at work (or at least I hope we are), why not at least just turn the faucet on and make a good show of it. Add a little soap to it and it'd be even better. Strangely, I've noticed that managers, directors and various other higher-ups are the biggest offenders. At least in my lame company (and the company in the suite next to us).
And a related gripe...public restrooms that don't have the trash can near the door and/or it isn't an open-top trash can. Because of the problem above, I use a paper towel to open the door when leaving, then prop it with my foot and toss the used (dirty) towel in the trash can. If there's no trash can near or I can't toss the towel, I have to take the dirty towel with me. Ick.
Actually, while I'm talking about public restrooms, they really should have some sort of background music playing in all public restrooms. I really don't like hearing someone struggling in the stall, and the gruntin' and kerplunkin' that usually accompanies it.
And an unrelated peeve. Sick kids. Not just because it's miserable seeing them miserable, but because as a parent you just gotta kiss and hug on 'em no matter how sick they are, which will eventually get you sick, too.