Can't snap my fingers or whistle. The closest to a whistle I get is this weird, weak, high-pitched tone I press through my teeth.
And obviously, the most common one - I can't dance. And I effing HATE being told "you just have to try it, you'll like it!". Because you know what? How about I take you to a shooting range, and you will have to shoot at stuff for two hours. What, you still don't like it and you're not good at it? Oh, you just have to try it some more!
OF COURSE it will be more fun once I get better at it, but even so I just don't WANT to get better at it - I don't enjoy it!
This argument comes up for NO OTHER hobby! I can't tell you you should start Magic: The Gathering, and that no matter how much you hate playing it, it will be fun once you do it long enough, so don't tell me the same about rhythmically moving my flesh across a dance floor! Sorry for the rant.
Other than that, I have a real problem expressing sympathy in case of a sad event, something most people find natural. It's not that I don't feel sympathy, I just don't know how my face is supposed to move to convey it. I never figured that out.
EDIT: Also, reading through this: opening beer bottles with anything BUT an opener. People don't even trust me with trying anymore. They'll just automatically open my beer for me because I always break stuff or hurt people when I use something else.