http://fsharp.org/testimonials/#tabbles-1 Completely in F# see comments above
http://www.rawbots.net/ are using F# in a very significant way and are in the process of making it their primary language.
http://fsharp.org/testimonials/#path-of-go whole AI logic in F#
http://fsharp.org/testimonials/#yan-cui backend in F#
http://www.galaxywarsthegame.com/ uses F# entirely
http://www.assettocorsa.net/ uses F# to prototype their vehicle dynamics.
and many more here http://fsharp.org/testimonials/