A falchion/scimitar/etc. curved weapon+10 will make Quelaags furysword, an incredibly powerful fire weapon.
an Uchigatana/Iaito/Washing pole+10 will make a Chaos Blade, a powerful weapon that eats 20 of your health per swing.
The Quelaags Furysword looks amazing, and has a good wide angle move set. It also glows with fire as you swing it. Both weapons scale damage with humanity. --- Read the following sentence twice: The lion has eaten the gazelle.