Masters of Unique weapons (5e Monk-Artificer multiclass mix)
by Marc SaindonThis is a simple idea of a build that allows an Artificer to design a unique weapon (e.g. a "flying guillotine", which is a chakram, with a special critical - decapitation - and a returning effect) and have the Fighter or Monk martial skills to wield it efficiently. The key word is 'unique', and the interest is less with overpower than just give a PC or a NPC a special trait that sets him apart (upon seeing the corpses, the guards say "this could ONLY be the work of the Master of the Flying Guillotine").The whip-sword (urumi) would be another possible weapon, some variant of the war fan, or maybe an odd object like a rake or flute could have been crafted for deadlier effect (see arms of wushu in notes). This would definitively require some homebrew, but you could create the deadly assassin known as "the Final Note" who kills with a flute.
Notes:
Urumi
Japanese war fan
Eighteen Arms of Wushu
(Image from: https://www.deviantart.com/ubermonster/art/Flying-Guillotine-concept-sketch-315178641)