Well, it's definitely not this! (Cornelissen's MAGMA.)
I love the label on Haut Brion. (And almost always, the wine inside.)
I also love the labels on Egon Muller and Willi Schaefer's bottles. Both very elegant and understated.
FX's Unendlich is also pretty cool, though in a very different way.
Also, I might be inclined to agree with tooch on how lovely the Overnoy labels look, but it'd be nice if I could actually see one in person (or in my cellar) a bit more often.