If you could permanently alter one thing about your physical appearance, what would you change?

This should be a very simple question to answer. Who doesn't constantly think of something about the way they look that they wish they could change? The most gorgeous and perfect people on the planet are still insecure about something. The only tricky thing here is choosing one thing. Like most women, there are several things I'd like to change about myself. I have 5 birthmarks. FIVE. I have terribly frizzy hair, I am overweight, I have thick ankles (even when not overweight), I have acne...STILL! However, I've learned to live with too many birthmarks, I know how to fix my hair temporarily, I can lose weight, I never wear shorts so no one ever sees my ankles, and I know how to cover acne with make up. There is one thing that I will never be able to ignore or get rid of though. Stretch marks. I don't have them as bad as some women. Some poor souls have developed stretch marks all over their bodies from pregnancy. I only have some on my stomach, as most common. I hate them though. I absolutely hate them. They almost make me feel as if there is no point in losing weight because I'll never be able to wear a 2 piece swimsuit anyway. I suppose there are surgeries to fix stretch marks, but I'll never do anything like that. Aside from not having the means, I have a fear of unnecessary surgery. I could just knock out acne, horrid paleness AND stretch marks by saying I would change my skin. I like the freckles and I love my tattoos, the rest of it can be totally different.