The most fun I ever had was writing Gravity Force, based on that great Danish Amiga title of the same name.
It is different of course, but it is great fun to play. It isn't finished, but it's worth a go!
Click here to download the Win32 MSI for Gravity Force X
And in the spirit of Open Source, here is the source code for Gravity Force X. I think I used DirectX 8 and Microsoft's C++
Visual Studio version 6.0. I think I'd make a great game if someone could spend their time updating it!
It used an old game system I wrote back in the day - and in terms of quality was lots better than my War Games Construction kit.