Here's a great cheat for Slap Fight. Insert a
credit and select 1 player. When you begin the
level, just sit there - don't kill anything.
Let your player be destroyed. When you begin
again, you'll have all weapons and powerups!
If you don't fire at all, but dodge your way
through the enemy shots as long as possible,
you'll get a big bonus and start your next life
just before the second big boss. You have to get
as far as the ring shaped pool to get this.