Call of Duty - Call of Duty is a first-person and third-person shooter series by Infinity Ward.
PunchLab - Track the strikes you throw at the punching bag
Unreal Tournament - Unreal is a series of first-person shooter video games developed by Epic Games.
Timerly - A real interval timer
Xonotic - Xonotic is a free (GPL), fast-paced first-person shooter that works on Windows, OS X and Linux.
Liteboxer - An at-home boxing solution