I'm a teen and I work in an ice cream truck. I need a good comeback for when people make fun of me?

You do not need a comeback. People are trying to share a joke with you. Be polite and laugh at their jokes. They desperately need a kind word from you. The best thing to say is something like "You've got some good material." -- NOT "You're a good comedian." Never give anyone a direct compliment, and no comebacks at all.