Do we have a list of active wargs? Is it just Bran, kind-of Arya, and kind-of Jon?
I've always wondered if Robb warged into Grey Wind as he was killed, or if Howland Reed is a warg.
Well Robb is kind of a non-issue because even if he did, he's dead.
Then there's the warg/skinchanger issue...
Bran is both a warg and a skinchanger. He spends his time in Summer, Ravens, Hodor, Trees...
Arya is a warg, but as far as I'm aware she's only in the passenger stage with Nymeria (she has the wolf dreams, I don't think she's ever controlled her). She's also a skinchanger because we've seen her cheating on her test using the cat, which she did control to get it up there in the first place.
Jon is a warg. He has both controlled and passengered Ghost. We haven't seen him inhabit anything else.
Rickon is probably warging into cannibal unicorns as we speak but we've never seen evidence of it. He had some of the same dreams as Bran though (they both went down to the crypts to investigate the same dream).
We have no idea about Sansa because Lady was executed and as far as we know she hasn't tried with anything else. I'm not sure it would even occur to her (though I wouldn't be surprised to find her skinchanging into a birds or something later).
Tormund had a skinchanger amongst his wildlings I think, with a boar?
As Varamyr had been to some sort of Skinchangers meeting we know there are more out there somewhere, so there's probably at least a couple mixed in with all those wildlings somewhere (and while no longer a skinchanger, the remnants of Varamyr's mind are in that wolf in Summer's pack)
And Bloodraven is Bloodraven. I'm not entirely sure what he counts as at this stage.
Poor Davos (...or Shireen?) needs some penmanship classes. At least I hope it's one of them. If Stannis writes like that... Ah well, at least Kings mostly just stamp things.