Carrot cutter 

Someone who is so dumb the only job suitable for them is cutting carrots.

Joe over there failed his math test, he's for sure destined to be a carrot cutter

Or

You had one job you f**kn carrot cutter!

Carrot cutter by Claudius trufflescale May 31, 2020

carrot cutters 

Large, protruding front teeth similar to those of a rabbit.

"Did you see the carrot cutters on that guy?"
"Yeah. Those are some awfully big Chiclets for such a small pie hole."

carrot cutters by D Breezy February 3, 2009