Read a short piece of work for Dungeon and Dragons (5E) about using it as an Urban Fantasy system. Good article, if way too brief. There was the promise of additional articles to follow.
What made it stand out for me was the image of a Warlock using the pact weapon ability to shunt away a pistol. If you are unfamiliar the Pact Weapon can be called immediately to hand through use of this ability. Suddenly a whole cascade of images filled my mind, swamping my ability to think for the evening. Half Orc taxi drivers, Elves in suits, street ninjas. I found it very inspirational.
The bad news is that it caused that other game designer (and other creative endeavor) mental delusion, the belief that there is no point to what you are creating. Why should you bother making a whole new thing, when there are already so many things similar to yours?
I know it shall pass, but in the meantime if you have any tricks for overcoming this feel free to share.