This ZIP file includes the .STLs needed to print a desktop Basketball and desktop Football game easily with a 3D printer.
 
Assembly of the Ball Launch and the Halfcourt/Endzone is very easy.  The 'T' at the end of the launch fits into the Halfcourt/Endzone with the bowl of the launcher sitting on top of a small edge to create the potential energy needed to launch the ball into the target.
 
However, the ball launch is made to fit pretty snug; so, if it prints with a lip from the 3D printer being used, that extra plastic may need to be shaved off with a razor.