For an assessment at university, we were tasked with creating a 3D game using Microsoft's XNA framework. After many iterations of various games, I settled on creating a firing range shooter. The focus was mainly on the weapon handling (e.g. aim down sights, recoil). My experience working with XNA has taught me how easy it is to hypothetically shoot yourself in the foot when you start to rely upon frameworks that are designed to be highly abstracted. This project especially taught me how important planning is, as I went through roughly six plans (ranging from flight sims to a Minecraft clone) until I ended up with the final product.
Binaries can be downloaded here. You will need the XNA 4 Runtime.