F# and MonoGame on the Mac. If you want to build games on the Mac, you have an interesting option with MonoGames. This is a reimplementation of the Microsoft XNA APIs. So basically, it's just the continuation of Mono into the gaming area. Pretty cool stuff - and because a cool thing alone isn't enough, the linked article provides the whole thing with integration in F#, the functional language for .NET from Microsoft. Unfortunately, for iOS, MonoTouch and for Android, MonoDroid are required, which means there is a slight hurdle to overcome in terms of acquisition (the licenses are not exactly cheap, so maybe not quite the knockout for hobbyists).