The Elucidator
Elucidator was first introduced when Lisbeth checked its name, to find it was not a player made weapon but a boss drop, and Kirito requested a blade of equal quality, hence the Dark Repulser. It was then used to test the strength of Lisbeth's best sword, which broke upon striking Elucidator, which meant this was quite a strong weapon and Kirito has used it quite often.
