Combat pet

World of Warcraft provides two primary combat pet classes: hunter pets and warlock pets. In the Burning Crusade, other classes can summon pets. Mages can summon water elementals, priests can summon shadowfiends, shamans can summon spirit wolves as well as create fire elementals and earth elementals by summoning totems, druids can summon treants, and Death Knights can summon a Ghoul.

Death Knight
Death Knights get the ability to summon a temporary ghoul if they choose any talent specialization other than Unholy. If a Death Knight chooses to use Unholy as their primary talent tree, they get the Master of Ghouls Talent which allows them to summon a permanent Ghoul once every two minutes.

Hunter
Hunters must tame wild beasts so that they can become their pets.

The hunter's pet is his or her constant companion as he or she travels through Azeroth. The pet usually acts as a tank when the hunter solos, allowing the hunter to maintain the range hunters require to do their best in battle.

(See also, Hunter pets 3.0.2 changes)

Warlock
The warlock can learn spells to summon minions to his command (see Warlock Spells).

Warlocks have the ability to summon or enslave demons under their control.

Warlocks gain the ability to summon an Imp demon early in the game through a quest. Imps are not proficient at melee combat (due to the fact that they are completely incapable of performing a melee attack), and are mainly useful for assisting your party from a range.

The Warlock can gain the ability to summon other demons as pets through quests. Each pet quest has a level limit on it — players may not attempt the quest until they have reached the required level. The voidwalker quest is received at level 10. The succubus quest begins at 20, felhunter at 30, infernal at 50, and doomguard at 60. The felguard becomes available with the appropriate 41-point Demonology talent.