Wracking balls

Punching someone testicles.

My brother kept wracking balls when we were younger. It was pretty weird and very painful.

wracking his brian

An euphemism for a male masturbating.

We thought the OP meant he was trying to remember something, but after he slipped and linked us to the site he was visiting we realized "wracking his brian" meant he was jacking off!

Wrack

Hit your head on something.

Ow I wracked on the wall.