Petopia has posted a Ghost Saber gallery, featuring pictures of, as far as I know, the only translucent pet in the game. It looks like it's stealthed, but to everyone, all the time (of course, when it's stealthed to other players, it's invisible to them, but you know what I mean). The gallery has some fun shots of this very unique pet.
Petopia promises a "how to" on where to get your own soon, but if you don't want to wait, apparently it spawns at level 19 or 20 from "Glowing Cat Figurines" in the northernmost Naga area in Darkshore. Find cat figurines on the ground (Dwarven treasure tracking will find them, apparently), open them up, and there's a chance that the Ghost Saber will spawn. Tame him and he's yours. He may die soon afterwards (since the spawn has a usual despawn time), but even if he does, you can simple ressurrect him as long as you've tamed him as your pet.
The low level of the pet, unfortunately, doesn't really make it easy for hunters who are already high level (since to get this guy up to 70 from 20 would just take way too long). But if you find one that's 19, it's perfect for battleground twinks or up and coming Hunters who want a cool, different pet.