Hmmmm. I like the idea of having, well, just about anything suggested so far . . . but for the sake of originality, I'll say the One Ring. Unless its corrupting powers still work here (
!), in which case I would say . . . an actual copy of the Red Book of Westmarch! Ooh, that'd be better than the Ring anyway. Set right what Tolkien got wrong, and all that.
Or, wait, what about a crate of Morgul-blades? Would that work? I mean, technically it's more than one object, but so is, say, a
pair of hobbit-shoes. Plus, I could stab all my least favorite people with them and turn them into my wraith-slaves . . . or just hang them up on my wall (the blades, not the people!)
Or maybe Legolas' bow? Along with the Infinite Quiver (TM) from the movies, of course. Hmm, perhaps the Arkenstone - though preferably without the angry Thorin threatening to throw me over a cliff.
Too . . . many . . . things!