GUNSMOKE

Unlimited ammo:
On the title screen, press Right, Right, Right, Right, Select,
Select, Select, Select, Right, Right and then begin the game.
You'll be given a machine gun with plenty of ammo to help you
rid the townshpis of pesky bandits

To start with rapid fire power:at the title screen press A(4x), Select (4x), 
R,R, Start.