When people bring up things you don’t want to deal with – for example teasing you about something you don’t want to be teased about – just make the situation intensely awkward. They won’t mention it again. 

Similarly, if people insist you do something you don’t want to do because “it’ll be fun”, make sure you do such a weak, half-arsed job of it that it’s obvious you’re not enjoying it at all and everyone gets embarrassed they asked. That’ll learn ‘em.