Gun.Smoke is one of those games that's a self-scrolling shooting game, but with cowboys instead of flying machines. You start off pretty weak (natch) and have to slowly walk forward shooting the bad cowboys and buying guns from the townsfolk.
But, what if you went to the title screen
And quickly pressed
A, A, A, A, Select, Select, Select, Select, Right, Right, Start
And then checked your inventory?
You'd have a machine gun to do anything you want with.
Me, I like mowing down everyone in the first level with it.