Originally Posted by EvilMike

Though I neglected to mention, it would also have an interesting use in SP levels. Aside from being the most powerful weapon by far (the other shields are more defensive in SP, and the water shield isn't as much of a superweapon), it is also capable of some unique tricks like destroying pretty much any object/scenery through walls. It could be used, for example, to destroy a crate buried deep within a wall.