Pronounced "kai-meh-ra," this mythical mish-mash of different animals has a Froststorm Breath ability, which does a bit of damage slows down your enemy by 50% for 5 seconds. Normally the cooldown is 10 seconds, which in itself isn't that bad, but with the Beast Mastery talent Longevity, you can shorten this to 7 seconds. Combined with well timed Concussive Shots, you could keep an enemy slowed to 50% speed for 12 out of every 14 seconds. That makes this pet one of your best bets kiting, and excellent for PvP: if melee types like rogues and warriors keep slowing you down with their hamstrings and crippling poisons, this beast is your revenge. It won't free you if you're snared, but it will snare them and give you some hope of escape. It's a Cunning pet, so it's extra mobile, and it can also help you recharge your mana in a fix, but it may not have some of the extra damage capabilities or survivability of Ferocity and Tenacity pets.
Check out BRK's video of a chimaera pet, have a look at Wowhead's chimaera gallery to see whether you prefer the Azerothian or Outland breeds, and then scan their list of tamable chimaeras to find the one nearest you, in many places, such as from Winterspring to Shadowmoon Valley.
If you're wondering what sort of normal pets have similar functionality, the next closest pet to the chimaera is the hyena, with Tendon Rip, which lasts 1 second more than the chimaera's ability, but has a 10-second longer cooldown.