Sibling Riflery (and other acts of random violence from my youth)

I say “I am gonna shoot you”
You say “I’ll catch the bullets with my teeth”
I say “I’m gonna kick in you in the kidney”
You say I haven’t got the reach
I say “I’m gonna head butt you, break your skull”
You say “You’ll come off second best”
I say “I’ll knock the breath out of your lungs”
You say “Ha! not with my rock-solid chest”
I say “I’ll karate kick your shins”
You say “Your foot will snap in half”
I say “I’ll lob a grenade and blow you up”
You say “through my impenetrable fortress? don’t make me laugh”
I say “I’ll knee you in the groin”
That shut you up