Borderlands' uncanny arsenal is probably its greatest strength, because it goes so very far beyond the standard ritual of FPS games: "Oh, a shotgun. Oh, a bigger shotgun." In Borderlands, it's "Oh, a shotgun. Oh, a bigger shotgun that shoots explosions." You get guns that shoot fire, lightning (haven't seen any shurikens yet, though), and acid. You get guns that shoot other guns. You get grenades that teleport to their destination, grenades that split into smaller grenades, grenades that explode on proximity, or grenades that do all of the above.