All classes can buy a non-combat pet, Cat, Snake, Prairie Dog, and Roach are the non-combat pets I've seen, (Not counting Panda, Diablo and Zerg for the CE bonus)
Hunters and Warlocks get pets.
Hunters must tame their pets in the wild and the pets level up with them and can be taught abilities as they level. You are limited to beast type animals and some are not tamable, Kodo are the first that come to mind. Pets need food to stay happy.
Warlocks summon their pets. They get an Imp at level 1, a void walker at level 10, a sucubuss at level 20. The pets automatically are the level of the warlock. Imps just cost mana to summon, all others take soul stones which the warlock gets by draining the life of a monster.
That is it for pet classes.
edit-spelling
Edited, Thu Nov 25 00:56:08 2004 by KithPine
Edited, Thu Nov 25 00:59:00 2004 by KithPine