You could do PNF stretches for any muscle….just learn the protocols (hold-relax, hold-relax-contract, etc.) and voila…..you've got limitless combinations. It's great for spasm as Phoenix mentioned, and is perhaps the fastest way to increase flexibility, and can also be used for strengthening. It should be noted though that the benefits of PNF (the neuromuscular trickery if you will) are also its downfall when using if for athletics. That is, it will deminish power output (at least in an acute sense) more than any of the other stretching protocols.