I found that and decided to share with the rest of the world:
There's a Crocolisk in Sholazar Basin Ravenous Mangal Crocolisk - NPC - World of Warcraft
With a abillity without CD or GCD Jagged Tooth Snap - Spell - World of Warcraft
In order to get him to use it a cople times per second, you need to drag Bite and That spell to your pet's skill bar, then DISABLE Bite Autocast (You might need to Enable and Disable it a couple of times in order to get it working properly) and ENABLE Jagged Tooth Snap's one. You have to do that everytime you log in the game.
You may also want to spec in BM and put some talents that increase pet's Health and Armor, so it won't get killed too fast in BGs. And Don't forget to level it up!
Be aware that it MIGHT take a few tries, but It's worth spending time doing this, as you will be able to kill casters before they can say "WTF is that pet?!"
Also, in some servers, you will need to get the quest: Just Following Orders - Quest - World of Warcraft In order to see it. That doesn't happens in the server I play, though.
Happy Exploiting!
NEW PET!
Shadowmoon Riding Hound - NPC - World of Warcraft
It's in BT! Now, you need either to clear half of BT or to fly hack. The choice is yours. It doesn't matter the way you choose, the reward is great!
Enrage - Spell - World of Warcraft - Increases damage by 10% and Haste by 30 (Don't put in auto-cast)
Charge - Spell - World of Warcraft - Normal damage + 1300 + STUN! (Put that in Auto-cast, FFS)
Carnivorous Bite - Spell - World of Warcraft - Does 417 to 483 Damage every 3 seconds. Can stack 5 times. Does 11K damage at full stack, IDK why. (You don't have to put that in auto-cast, if you don't feel like.)
New Pet!
Lapress - NPC - World of Warcraft
Yet, another pet arises from nowhere! This one, is not a big deal, but it's harder to detect this one's bug. It has a spell called Frenzy Effect - Spell - World of Warcraft - Increases Atack speed by 30% . It's passive, always active, not on pet's spellbook and procs on every hit.
New Pet!
Longsnout - NPC - World of Warcraft
No, Seriously, this is the best pet that could ever exist in the world of online games! It can heal, damage, tank, kill, pwn, decrease target stats, reflect spells, and even make portals! It's a must have for any pro exploiter out there.
Some of his abilities includes:
Renew - Spell - World of Warcraft - heal for 2828 to 3172 every 3 seconds for 15 seconds
Slow - Spell - World of Warcraft - Reduces movement speed by 60%, and Attack and casting speed by 35%
Wing Buffet - Spell - World of Warcraft -Does 9000 to 15000 damage to enemies in a cone in front of the caster, decrease their speed by 50% and knock them back
Encasing Webs - Spell - World of Warcraft - Immobilizes an enemy and increases the time between its attacks by 100% for 6 sec
All the 126 Spells can be seen here: Longsnout - NPC - World of Warcraft
EDIT: They've fixed this pet, but just a bit. It still kick ass.
http://www.wowhead.com/?spell=60204 - 1600 Arcane damage every 1 second for 4 seconds.
http://www.wowhead.com/?spell=52719 - Weapon damage Plus 3 seconds stun.
http://www.wowhead.com/?spell=60158 - 5 Seconds spell reflection.
http://www.wowhead.com/?spell=60205 - 3325 to 3675 damage in 10 yards plus 100 yards knockback.
http://www.wowhead.com/?spell=6268 - Increase movement speed by 60% plus 10 more damage on next attack.
http://www.wowhead.com/?spell=41057 - 100% damage to enemies in 8 yards
WARNING: Continuous use of this pet may cause lost of account, pet dependency, family problems and social instabillity.
P.S. None of those abilities have CD or GCD (Except for some) ! Use and Abuse!