That's a good idea, I'll try those on thursday. I also like to do hexhead-dumbell holds. Hold the end of a hexhead dumbell in one hand by grasping the head only. Keep your fingers off the #'s and let hang them down next to you for time. I use 30's to 35's for time. I have small hands so I have trouble w/ anything bigger. I also like to do plate holds where you take two plates of the same size and pinch them together for time. you can do as many sets as you like until failure.
A great place to read is diesel crew, these guys do alot of crazy grip shit.