Gilgamesh's Noble Phantasm in Fate/Stay Night, which takes the form of a large, colored field behind him, with many swords of all kinds emerging out of it in ripples, ready to be launched. Often a chain, Enkidu, is seen shooting out of it, and is used to restrain his enemies.
Archer's Unlimited Blade Works is similar in nature, but uses copies of legendary swords. Gate of Babylon uses the originals. The fact that it produces so many swords also spawned the response, "King of Heroes, do you have enough swords?"
This tag is also used to refer to images that either reference this or involve a character spawning many weapons or other objects.