While this isn't the most interesting visually its actually an implementation of the platform layer from Handmade Hero in F# using SDL. I wanted to do something substantial using pure functional programming after John Carmack talked about his experiments with re-writing Wolfenstein and Doom in Haskell and Scheme (although I can't find the blog posts anymore?).
You can look at my (probably crappy) code here: https://github.com/tgaldi/FSharpHero
Handmade Hero: https://handmadehero.org/
Handmade Hero platform layer in FSharp.