What do you all think is an acceptable amount to tip at the AAFES Barber Shop?

It all depends on the barber and haircut result but I usually give a few dollars. I have given up to $5 or more at times for the same barbers I liked to have my hair cut. Sometimes a good conversation and listening to their stories will make me provide a better tip.

Couple of bucks.
I'll throw them a five if they are personable and do a great job.

I just go off post. You can get a better haircut, with less of a wait, for a couple dollars more. Or, "Happy Hour" if you're smart and it'll be the same price for a way better haircut.