It should just be part of the conversation... it's typically contrarian to what the conversation is discussing, or opposite of your stereotype.

If they're discussing alternative music, I say "uh, i like Taylor Swift". If they're discussing cars, I'd say I love minivans ("they're so useful!").

After reading the OP comment, saying my favorite language is Scheme is one I might try when talking programmers haha. In this case, I don't know anything about Scheme, so I'd see their reaction and just say I was just joking.