What is the best pet in World of Warcraft

Pets for Hunters in World of Warcraft fall in several categories; basically some are meant for DPS (Cats, Devilsaurs), Defense (Turtles, Crocolisks) or Spellcasting (Windserpents, Spirit Beasts).

Which type of pet you choose depends on what you want to use it for - the differences between pets within one family is not too great. Follow the related link to this question for a handy resource site for Hunter pets and their uses.

As for Warlocks, who are also a Pet class, which one you summon depends on what you use it for and what talents you have. In general Destruction prefers an Imp, Affliction prefers an Imp or Felhunter, Demonology prefers a Felguard or Imp. The SUccubus is used as Crowd Control and often in PvP, just as the Felhunter is.