ball brain

When you squeeze your nut sack and your testicles come up together and they look like a brain

Dude, check out my ball brain!

Balls No Brains

Something you either need massive balls to do or zero brains.

Example with no brains

Bobby “Why is that guy riding a motorcycle with no helmet at 130 mile per hour (209 Kilometers per hour)?”
Brandon “That’s because he has a bad case of Balls No Brains”

Example with huge balls

Bobby “damn! That guy just punched one of the robbers in the face, too bad he’s about to get shot.”
Brandon “That guys got a serious Balls No Brains way of thinking.”