I'm a big fan of the Tabata protocol (20 seconds work, 10 seconds rest) and have used it for quite a few different lifts, including back squats, deadlifts, DB clean & press, and others. My newest favorite, though, is weighted jump rope double-unders. It's a B-I-T-C-H BITCH! Got a fave?
First person to say bicep curls loses.