Galaga: No enemies:

Shoot any of the ships as they go into formation in the first stage, except for the ships that arrive in the last wave. Once all the ships are in formation, isolate the first two (yellow/blue bees) on the left side (which were the first and last ships in the last wave). They are in the first column of bees on the left side. Kill all the other ships except these two bees. After all the other ships are gone, allow the two bees fly and shoot at you for the next 10-20 minutes. Do not shoot during this time, and stay towards the right-hand side of the screen. After some time, both bees will stop shooting. Allow the bees to finish 3 to 5 more passes, then kill them. From this point on, ships in the game will no longer shoot. Additionally, if you lose a life later and are playing in two player mode, the other player also will not get shot at.