I was grinding on my priest, and didn't realize he was a rare spawn, so I killed him and got some pretty good gear.
For a pet, I personally prefer a boar for PvE because of the tanking abilities, and a spider for PvP because everyone seems to have arachnophobia.
My hunter has a Scarred Crag Boar, and Naraxis, both lvl 27 as of July 8 2008.