Have you designed one before? Have you played any? Do you have any favorites?
I'll start: I've designed more diceless games than dice-driven games; I tend toward using cards, particularly Tarot cards, for my designs, but I'm also working on one that's inspired by Choose Your Own Adventure games combined with resource management, and I also have a game in the pipeline that uses hands of futhark runes for resolution. My favorite diceless game, and perhaps just favorite RPG of all time, is Jenna Moran's Nobilis (specifically the second edition), although I will defend the obscure diceless Marvel Universe RPG from 2003 as a better game than it gets credit for.