[Shadow Kira01]

Archer's fighting abilities can almost be called copycats as that he doesn't have any originals.

Spoiler:

Unlimited Blade Works is generally the fake version of Gilgamesh's special attack as that Shiro has a similar ability to Sharingan of the Uchiha clan. After the battle with Gilgamesh in which Shiro was easily defeated, he learned to image that attack and it became Unlimited Blade Works but unlike Gilgamesh, those weapons are not the real thing but only copies that will disappear very quickly as his mana depletes.

Kanshou & Bakuya are generally the dual swords which Shiro image due to his encounter with Archer. In other words, these pair of unique dual swords is a creation born out of the time loop. If Archer never went back in time, Shiro would never have seen the blades to image it and thus, Archer wouldn't be using it..

Caladbolg II is generally a fusion image of Gilgamesh's sword and Lancer's Gae Bolg.

Although this makes Archer looks lame but oh well...