Cabal is a shoot-em-up, but it's not the kind of shooter that is seen much on the NES.  In this game you fire over the shoulder at all sorts of enemies soldiers, as well as pretty much anything standing in front of them, then do a happy dance once the path is cleared.  The controls are a bit different and take time to master, but I think it's worth it for all the destruction you get to render.  As a bonus, the game wasn't too hard to finish.

Review: http://takeontheneslibrary.com/finished/135-cabal/