Well, I am on a bit of an oud kick, so "Pure Oud" for sure. Though, it depends how the oud note is done. If it smells chemical like in Private Collection's Oud Wood, then count me out. If it smells overly dry and spicy like in Al Oudh, I will pass. If it smells like the oud in M7 though, then sign me up!!
If I was ever fed up with oud (which I doubt I will ever be, because of its rarity making it hard to find/smell) I would have voted for Pure Leather.
Pure Tobacco might be good too.. and I don't mean Pure Havane, where I get little to no tobacco out of.