knock you a good one

Punch the other person so hard they fall

I'll knock you a good one

good one

A good one is a sarcastically spoken term used to describe someone that is being/or is a big douche bag, an idiot, a cheater, a liar, a dumbass, or someone that is an outright fuck tard.

"Did you see that guy over there that thinks he's cool , but he only has 2 teeth? "That guy is a freaking good one! I would never date a good one such as that !

have a good one

Something said when the person is not interested in speaking to you any longer. Often accompanied by disinterested body language

DoorDasher: thank you
Employee: have a good one