Best Grip trainers

Looking to get a grip trainer to try and maintain some strength as I broke my clavicle last night mountain biking. Anyone have any recommendations for good ones to build/maintain grip strength. Something that lets you work opposing muscles would be great too to keep the elbows happy.

Thanks

Brett

Power Putty is absolutely the most versatile grip trainer I've found.

Jim Titt has some good suggestions on the Retiring Ropes thread...

I use the Black Diamond power ring and I get a pretty good pump after a closing and opening my hands a few times but leaves a rubbery smell on my hand afterwards.