I'm 15. People have told me I look seventeen, but that's only when I havn't shaved and my mustache and poor excuse for a beard grow out.
Annoyed: No, I quite enjoy it actually =)
Flattered: Yes, I like people to think I'm older than I really am. It helps when you have an opinion because the younger you are and people know that, the less likely they are to take what you say seriously.
Stories: Me and my family were walking down a street in New Orleans and a stripper walked up to me asking if I wanted a private show XD My mom was pissed and asked how old she thought I was, the stripper answered, "Sweetie, don't get huffy over your little boy-toy. He looks 18 to me." I laughed so hard after that. My dad was using a restroom in a bar nearby so he didn't know what happened.
Another time I was on a cruise for the summer and it had a program for kids. So I went to register for the Teens group and the lady manning the registrations looked at me and said, "I'm sorry, sir. Are you lost? Registration for Teens ages 15-17 are over there." I ask how old she thought I was and she said I looked 17.