Ironback

Ironback is a level 31 non-aggressive rare grey and purple turtle that can be found in eastern Hinterlands by the shore north of Revantusk Village. He has only one spawn location and he does not patrol away from it; specifically he spawns right near a troll hut and just sort of wanders around between the hut and the ocean. I have marked his spawn location in red on the map below. 

He drops the typical green item and a fairly decent amount of experience for leveling characters.

He would also make a nice hunter pet. The only other tamable turtles of this coloration are the level 35-36 Mudrock Spikeshells in Dustwallow Marsh, and the level 6-7 Marsh Snappers in Gilneas which can only be accessed by worgen.

Ironback can be found with NPCScan, but it really isn't necessary as he doesn't patrol very much. If you do want to add it, his NPCScan ID is 8213.

Before the Cataclysm his spawn timer was somewhere between 10-16 hours. I am not sure if this is still the case, but my guess is that it has been drastically reduced like most rares have been in Cataclysm.