Revive Pet

"Where is my Revive Pet?"

As of 6.0.2, Revive Pet and Mend Pet are integrated into one spot on your action bar.

Basically what this means, is that if your pet is alive, the button will show "Mend Pet". But if your pet has died, that same button turns into "Revive Pet". Very useful, especially when you are in a tough battle, when you click the button, if the pet has just died, instead it will revive your pet.

I was having issues at first with it, so I deleted both of the existing buttons "Mend Pet" and "Revive Pet" and then I pulled the "Revive Pet" out of the Spellbook and put it into my bar and that fixed the issues.

***Wanted to add something, in case you don't notice right away, the cast time for this command is 2 seconds, down from 4 seconds. Even the 4 seconds was wonderful compared to the way it used to be (considerably longer), but as 2 seconds, it's awesome!

EDIT: As of 7.0, for those who are wondering "Oh no, where is my Mend Pet/Revive Pet at?", do not fret. Blizz has put it into the "Pet Utility" button. Thankfully, if you don't care for how that is set up, you can remove the individual ability from the Pet Utility button and place that on your task bar to individually click it, instead of having to use a drop down (or drop side/up) ability.

The fact that there's no longer any way to reduce the cast time of this spell (aside from haste, which does affect it) is very disappointing - used to be you could spec into Improved Revive Pet and actually be able to res your pet in a reasonable amount of time. Nowadays, if your pet dies in combat you're pretty much screwed. Even with the pushback reduction from the glyph, it takes almost 10sec to use Revive Pet. If you're in a fight where you need to move, it makes this nearly impossible, so often if your pet dies you're simply stuck without a pet for the rest of the battle.

With the release of Patch 5.4.2, Dismiss Pet is no longer usable in Arena, and to counteract this "nerf," the casting time of Revive Pet has been reduced to 2 seconds baseline, and is affected by haste.
Also worthy of note if you were unaware, is that you can use deterrence before casting revive pet, safely ensuring your companion will rise from the dead.