Shit or get off the pot/fence (make a decision)
When god gave out brains, you got trains
Strong like a bull, dumb like a tractor
A couple of crayolas short of a box
Not the sharpest tool in the shed
Fell out of the ugly tree and hit every branch on the way down
Petty is as pretty does
An ass like 2 dogs fighting over a bone (not sure if that was a good thing or bad one)