When a girl is giving a guy a really good blow job, and after a few minutes into it she stops and punches him as hard as she can in the balls.
Tell a guy you want to give him a blow job, after he pulls down his pants wait a few seconds and give him a SUPER punch to the balls.
My boyfriend wouldn't stop playing video games so I gave him a punchkin.
A small annoying dog, often of the chiwawa breed or similar. Essentially suming up the regular definition in Dog form as in something a wife or girlfriend would buy to metaphorically punch the husband/boyfriend in the balls on a daily basis.
Guy walking a chiwawa down the street, "haha look at that punchkin"