What pet to get to 25?

[Symphonic]

There really is only ONE answer to that question: ALL OF THEM...

But in the process, you'll need the following:
- Anubisath Idol
- Mechanical Pandaren Dragon
- Terrible Turnip or Molten Corgi (needed for capture team as they don't kill the opponent)
- A moth
- A rabbit or hare
- Pandaren Water Spirit
- Chrominius

Well, I got my Molten Corgi to 25, and I have a Chrominus, I may use my 2nd item to level it to 25 immediately. We'll see.

[Val the Moofia Boss]

Fastest way to pet level?

Draenor pet tamers. Lead with the pet you wish to level up and then immediately switch out to your level 25s. You will be disadvantaged however, because your effectively going to be fighting a 2v3 and giving the enemy a free turn.

If you do not have a team capable of taking on the pet tamers, then simple level 25 wild pet battles in Tanaan will be the next best thing.

[Caanrial]

You can also get Patchwerk (I think that's his name) the dog from Naxx and he does the same thing as Chrominius *except* since he is undead he will handle a huge crit. This is important for at least one of the Draenor legendary pet battles that is heavily RNG dependent. Several of the arctic foxes & foxlings are great helpers as well since they have Howl (like Chrominius and Patchwerk) but also have Dazzling Dance which gives a big speed increase to all of your pets, so he is good to start with then switch over to the P/P breeds to kill things fast.

EDIT: don't forget about the combo of three ravens or crows. They will take almost every non-legendary PVE battle, plus many PVP ones too.

[Dinobull]

Magical Crawdad duh

[Ermelloth]

I'd add Nether Faerie Dragon and Unborn Val'kyr to the list.