Quick question for German Speakers

I'm looking for an appropriate German word to address a twelve-year-old boy that you don't know. The boy looks a bit older than his actual age and can pass for 14, so I don't want anything too babyish. The speaker is older and also male, in case that makes a difference.

English equivalents would be addressing someone as "Kid" or "Sport." In this specific scene, "Tiger" might also be appropriate as the kid is angry and the amused adult is trying to calm him down.

Thanks in advance!

I think Hitzkopf will work perfectly for the scene. Thanks so much for the help everybody!

(This is one situation where Google translate was utterly useless).