Emperor Crab

Honestly, this guy (in P/P breed) is my favorite pet for wild pet fights and pvp. You can stay at full health using Shell Shield and Renewing Mists. Shell Shield completely blocks most flock abilities and dots. Some fights can be a little slow since your Surge only does 282 dmg. 

If you are leveling pets just throw on Renewing Mists before swapping them in, helps keep them topped off.

@Khorghast

Short answer: Because of breeds. Emperor Crab is the only variation that can be P/P.

At 357 Power, it can dish out solid damage. Not great, since it doesn't have any inherently strong attacks outside of Whirlpool (which you shouldn't use as I'll explain later) but it's good.

Its true strength lies in the combination of Shell Shield and its healing ability. It just survives for ages, since both the damage reduce and the heal scale with its massive Power.

Why is this crab rated so highly when Strand Crawler and Shore Crab have identical abilities and are rated relatively low?  I'm pretty new to pet stuff.

I just picked one up.  They are often secondary pets to the horrible snails in the region. 

The P/P version guy is basically immune to DoTs with the combination of Shell Shield, his racial, and his powerful heal.

An extremely tanky pet, and one of my personal favorites. 

Went to hunt this pet today in preperation for the Pandaren Spirit Battles. First encounter was a rare, now he's part of my collection.

They call this pet the 'Emperor Crab' because the Mantid Empress got really, REALLY drunk one night and.. well....

I had two pets left to get in Pandaria - this and a crunchy scorpion. I went to the Dread Wastes to get my scorpion first and guess who popped up in my secondaries! Sadly he's only poor quality but I at least have the credit for the achievement... now to find another scorpion :-)

Really good pet. Very dependable with that shield. 

This is a must-have battle pet.

Not only can he solo most wild pet encounters and more than one trainer, I almost always run with him in my pvp team. Of course he is great against ele's and undead (spectral kid/unborn val'kyr can't touch him,) but he is shockingly good against flyers. His shell shield mitigates most of the dmg of abilities like slicing wind and his surge takes a lot of the punch out of alpha strike. The pets you do have to watch out for are ones with darkness/nocturnal strike.

Probably one of the best pets in my opinion. Fast, hits hard and has excellent heals. Great addition to any collection. 

I just found one next to the Lake of the Stars, right next to the wall.  He was secondary to a Clouded Hedgehog. 

I've been using this lil' buddy to help level the rest of my collection. He can take down all three opponents and stay at over 80% health. Because of this, I've been able to use lower level pets in higher battles and really speed up the leveling process. Love him! 

Found one spawned, and found several of different qualities as addons to the Rapana Whelks in the area surrounding Kaz'tik the Manipulator at 42.72.

This guy devastates Farmer Nishi.  Against first sunflower pet use almost any combo starting with Whirpool, Heal and Surge.  Against his second turnip pet; he will submerge for two rounds, so on your first move use Surge, then Whirpool and Heal yourself up.  Once he pops back up, that untasty turnip is basically just a nice soup for your Emp Crab. Hit his last beast pet with Whirlpool to keep things safe, then swap in low level pet to finish up, getting tons of exp.

Definitely a must have pet for PVE pet battlers, this pet can practically solo almost all of the MoP trainers (I use P/P breed, but H/H does fine as well). 357 attack power with the P/P breed! You have a wide assortment of attack/defensives to suit your needs (Surge for Elementals, Snap for Critters, Mist/Heal+Shield or Mist/Heal+Whirlpool). I carry 2x P/P breeds, and 1 H/H breed.

Absolutely love this guy. I have a P/P and, like the guy who named his Bane of Nishi, I use him to power level on both Nishi and Aki! I'd really like to get a second.

I got a 4, 14 (Destruction) breed of this guy and he's been one of my mainstays ever since.  Good mix of moves, and with his high damage/high healing, he's got great survivability, and he absolutely crushes Elemental pets with a Surge, Healing Wave, Whirlpool moveset.  Surge makes his high damage, low speed combo almost a non-factor, since you can always get off a finishing attack even against faster opponents.  Pop Whirlpool, Surge, Surge, and Healing Wave as needed :D

I have two lvl 25 rares, Constantine and Nero, that form the backbone of my Critter Gitter Mob. Pop in a low lvl pet to level up and they're able to deal with any wild trio I come across.