Beat the game on Expert to get the disruptor.
Hold Z and press Right, Left, Up, Down, A, B, Start when "Press Start" appears on the opening screen to access a debug menu.
The secret eighth level is accessed by finishing the previous seven levels on the "Hard" setting.
Shoot down the President:
Hold Z, C-up, and C-down during game play, then fire a homing cluster at an enemy plane. The president will jump out if the H-Cluster hits.
Thanks to Revolution readers Adam Bernhardt, Clifford Rediger, Brian Miller, Philip Neumann, Philip Mark, Greg Yanase, Joe, "Floating" Ryan Hamilton, David Cooper, and Chris Schmidt!