Here's what I use:
It's the standard PanaVise head with the clamp base. It's a great tool; I particularly like the fine-thread adjustment on the clamp and the soft-rubber jaws. I did, however, add a couple of loops of blue tape to the clamp-adjustment arm to keep it centered. I'm not a fan of the wood-bench-style sliding-arm tightener; the tape keeps the arm centered so I can spin the vise open or closed fairly easily with one finger.
Beware of the ball-and-socket joint in the base, too. Loosen it up too much and the whole top can drop over on its side. Again, there's probably a way for me to adapt the base to avoid this problem (like being more careful, or not adjusting the base with a model in the clamp). The tool is fantastically adaptable.
The company makes lots of head/base/ect. combinations: www.panavise.com.
Best of luck,
Matt Usher
Editor, FineScale Modeler