I am currently doing full-body workouts and give the bi's one exercise - standing BB curl. I'm doing slight cheat curls right now to try and bust through a plateau.
I know what you are talking about ... those doods that do 1,000,000 reps of various curls. Like they get to the gym and say, "Today will be a bicep day." And that's all they do.
The guys w/ the biggest guns at my gym seem to only do one exercise... standing BB curls. That's not why I do them, but seems interesting. Usually the little to mid sized gun guys are the ones doing 50 different variations w/ 20lb. DBs.
Edit: BTW, I had a pseudo-PR yesterday. I cheated my ass off, but I BB curled 135 twice. I did it just for the hell of it cause I already had the weight on the bar. I was really surprised that I even did it once.