I've been thinking about how it would be neat to have a unique sword focusing on Decapitate, concerning mainly frequency of use rather than damage (unlike Red Dragon's crit gimmick, in other words). A unique sword that sets Decapitate's cooldown to just one turn, or reduces the cooldown by 2 turns upon each killing blow dealt specifically with that sword, or even refreshes Decapitate's cooldown outright after successfully executing someone with it.
Honestly would be really cool if some of these features were integral to Decapitate to begin with, such as cooldown being decreased by 1 turn upon killing a living target with a sword attack, which the unique Executioner's Sword I'm talking about - or whatever it should be called - would then improve upon, one way or another. A potentially interesting alternative to Flurry spam, basically.