Mostly on mobile I would guess. Xamarin has a showcase on their site: http://xamarin.com/apps http://xamarin.com/apps . Also every game made in Unity is using

Mostly on mobile I would guess. Xamarin has a showcase on their site: http://xamarin.com/apps http://xamarin.com/apps . Also every game made in Unity is using Mono, which is _a lot_ of games. The Playstation Vita and Wii U uses Mono as well for third party development.