You can choose anyone who you look up to. It should be someone that you would want to be a few years down the road from now. You should explain who the person is, but more why you want to be like them and what about them makes you look up to them. They want to see what you admire in others and what your own aspirations are. Make sure you are showing both in your essay. You should be clever in choosing the person; it doesn’t have to be the most successful person in your life. Instead, maybe pick a more random person that you admire for things besides the size of their paycheck.
These are some programs that are popular among high school students. This is by no means an exhaustive list of nationally recognized programs. Boy’s/Girls States