Via Clemens Vasters, Vertigo Software has ported Quake II to managed C++:
Now, in July 2003, Vertigo Software, Inc. is releasing Quake II .NET, a port of the C-language based engine to Visual C++ with a .NET managed heads-up display. We did this to illustrate a point: one can easily port a large amount of C code to C++, and then run the whole application as a managed .NET application using the Microsoft Common Language Runtime (CLR) without noticeable performance delays. Once running as a .NET managed application, adding new features is easy and fun.
The radar feature is pretty slick!