First appearing as an 11-point Beastmastery talent, Master's Call is now a new baseline skill for Hunters in the Wrath Beta. With this skill, your pet will rush to your target and remove all existing movement impairing effects or stuns on the target, and cause them to be immune to them for 4 seconds. It can be used while you are stunned.
This is certainly a handy ability to have. In PvP, this should be awesome for getting away from Warriors and Rogues. In PvE, there's bound to be bosses and mobs with slow and stun effects, and this little skill could in theory, save a wipe.
One of the biggest secrets to using this skill effectively is probably going to be realizing that it can be used on your allies. If you find yourself not the center of attention, or if you have The Beast Within, you may very well find that it is a better use of your time to send your pet after your teammate. A mouseover macro'd Master's Call may be the perfect thing to save your healer from obliteration in Arena play.
The downside, of course, is that your pet needs to be alive and able to charge to your target to get off the effect. That means that you have one more reason to make sure your pet is properly protected or bolstered, be it via talents like Blood of the Rhino or Heart of the Phoenix, or a healer who isn't adverse to keeping an extra eye on it.
This spell, overall is still definitely a great addition to the Hunter's arsenal, and may go a long way to shoring up their dismal arena numbers. We'll be looking forward to playing around with it come Wrath of the Lich King.