Extra ships:

Press the D-pad at least fifty times in any direction during
demonstration mode. Begin game play and collect at least $10,000
before entering a shop. Nine ships may now be bought for $9,000.

Bonus points:

Hamburgers are worth $1000 during the first thirty seconds of level 1.

Unlimited laser, wide beam, and seven-way shot time:

Buy all the big engines (Big Wings, Jet Engine, Turbo Engine, and
Rocket Engine) before buying a weapon.