Just do 10 of the following:
[You may use the D-Pad or Analogue stick for the directions. The Machine Gun is mapped to the A button by default ('Layout A') or to the Right Trigger if using the 'Classic V8' control setting. You must have the required amount of ammo to pull off the charge-up attack.]
Rockets:
Roadrunner: UP DOWN DOWN + Machine Gun
Stampede: UP DOWN UP + Machine Gun
Longhorn: UP DOWN RIGHT+ Machine Gun
Missiles:
Afterburner: UP UP UP + Machine Gun
Halo Decoy: UP UP DOWN + Machine Gun
Patriot: UP UP RIGHT + Machine Gun
Cannon:
Cow Puncher: DOWN UP DOWN + Machine Gun
Buckshot: DOWN UP UP + Machine Gun
Ricochet: DOWN UP RIGHT + Machine Gun
Mortar:
Turtle Turnover: DOWN DOWN DOWN + Machine Gun
Tire Buster: DOWN DOWN RIGHT + Machine Gun
Fire Starter: DOWN DOWN UP + Machine Gun
Mines:
Bear Hug Mine: LEFT RIGHT DOWN + Machine Gun
Hover Mine: LEFT RIGHT RIGHT + Machine Gun
Cactus Patch: LEFT RIGHT UP + Machine Gun