The best weapon in the game is a highly subjective term. While Vermis is by far a freaking awesome weapon, I would have a hard time calling any given weapon the best. Mjolak has a crazy angry proc (and as an added bonus is a halberd for retarculous damage), Saal'thul is great for it's invisibility (and haste? I can't recall), flavorwise Turox just plain rocks (I mean come on, exploding mace!), and of course there's Neerc se'Ulb with it's lifedrain.
Other than that I have nothing to add to this thread.