It really depends on the circumstances and how Dean reacts; if he can’t see anything because it’s dark, and he hears Sam’s voice (no matter how loud and how distorted), he’s not going to strike out with gun or knife until he knows where Sam is and what’s going on. If it’s light out and Sam catches him off guard, he might get a cut on a finger from Dean lashing out instinctively.

Much figuring things out would happen afterwards, along with really big, hurt eyes from Sam if he got stabbed. oAo

Oh dear, poor Sam! And Dean’s a little small to be able to manage a nice style like they’d get at the hairdressers, so Sam’s hair will look a little choppy, and Dean never did manage to get it to spike up in the front.

(Still better than Dean putting Nair in the shampoo)

I think there’s no way Dean would get away with it, once Sam woke up and found out what Dean did, he’d get himself pocketed for the rest of that day.