Please remember one big thing - you don't want to use the stone prior to using a rare stone on the pet that you're leveling with the Ultimate stone. Why? Because you'll lose 2 levels when you upgrade it to rare. So, upgrade it to rare first, and then use the Ultimate stone; then you'll have a rare quality level 25 pet.
Another thing to note - these are my opinions. You'll see that some of my opinions overlap with other lists (like the ones that you see here and here), but some of them are just pets that I've found incredibly useful at one time or another. You can totally disagree with me if you think I'm way wrong.
- Darkmoon Zeppelin - strong mechanical with Decoy, which makes it that much better.
- Mechanical Pandaren Dragonling - versatile mechanical with dragon moves, and Decoy, because Decoy is awesome.
- Anubisath Idol - Incredibly versatile and huge tank when it comes to taking damage.
- Xu-Fu, Cub of Xuen - Great combo of Beast abilities, high attack
- Chrominius - best Magic pet, period - great for burst damage.
- Molten Corgi - Great for catching pets because of Superbark - also has fairly high speed for damage.
- Terrible Turnip - Also good for catching pets because of Weakening Blow, not really good for much else.
- Lil Ragnaros - Amazing for PvP - lots of burst damage and lots of defensive moves.
- Moth (any) - Moths are great for burst damage against any Aquatic type.
- Rabbit (any) - Having issues with Undead types? Rabbits with their Stampeded
- Gilnean Raven or Dread Hatchling - a flying type with Darkness and hard hitting abilities makes an awesome addition to any team.
- Zandalari Anklerender (or any of the Zandalari pets) - These delicious little beasts are known for having some of the highest attack, combo'd with some great Beast abilities.
- Sprite Darter Hatchling - If you've been reading the website for any period of time, you know I love this little guy because of Life Exchange.
- Hopling - One of the best Humanoid pets, with some of the highest speeds out there.
- Chuck or Muckbreath - I love these little Aquatic pets, mainly because of their beastly Rip + Blood in the Water combination
- Fishy - Another hard hitting Aquatic pet; he used to be able to solo the Grand Master Trainer in the Valley of the Four Winds before they changed the second pet.
- Pandaren Water Spirit - Part of the "Howl Bomb" combo of Unborn Valk, Chrominius, and this pet. I don't use Howl Bomb too often, but it's pretty sweet.
- Pebble - A versatile little elemental pet that's easy to get.
- Menagerie Custodian - Same skill set as the Darkmoon Tonk, but I like his balanced stats a little bit better.
- Pandaren Monk - Another Humanoid that packs a big punch - literally (I know, my jokes are horrible). He can hit really hard.
- Ghastly Kid - A new buddy for the lineup, but he's got a great combination of traits and abilities for being an Undead pet.
- Emerald Whelpling - Many people say that this is the best of the whelplings; I'm still not totally convinced, but it's definitely worth using your Ultimate Battle Stone on if you don't have to do so on any of the others I've listed here (I had that issue).
- Any of the Direhorns (Runt, Pygmy, or Stunted) - These Beasts are, in my opinion, some of the best in the game. With their Horn Attack (which has a chance to stun) and Trihorn charge (which lets them always go first - Quick Attack anyone?), it's a pretty hardcore little Beast
- Clockwork Gnome - This was my first pet that I leveled to 25, and he was a little beast. With his DoT and the other little tricks he has, he's pretty fantastic and a good first mechanical to have if you don't have one yet.
- Giant Bone Spider - Great for PvP because you can use the DoTs and the Death Grip to switch things around. I love it because of how much control it gives you over the game.
Do you agree with my list? Where do you disagree? And what do you think I should add to it?