Yamato, the sword of separation, wielded by the Legendary Dark Knight Sparda and his son Vergil. It is able to cut through anything, even concepts.
Sparda used it to separate the human and demon realm, and his son Vergil used it to separate his fears and his human half from himself, manifesting as their own beings, his human half V, his demon half Urizen and his fears as Nightmares.
Also, Yamato is often used to cut trough space, creating portals to another place or even realm.