You could get a nice wolf from the Hinterlands, or a scorpid from Tanaris, or a gorilla from stv. If you want to stick with a cat, King Bangalash (43 elite) will be tamable for you in another level (don't forget your freeze trap for taming). There is no one best pet, but some have special abilities like dash (my favorite), howl, screech, or prowl. It's up to you to pick what you like, but Petopia is a good resource:
http://petopia.brashendeavors.net/