Bonus Room: If you manage to get through the entire game without killing any civilians or letting the zombies kill any civilians, you will be rewarded with a bonus room, just before the last boss.
No Reloading On Final Boss: If you shoot your gun away from the screen 5 times right before fighting the final boss, you won't have to reload.
For a quick and painless reload, simply put your fingers in front of the nozzle and squeeze one off - then you can get back to killing whatever it was you were killing without interruption.
Quick Reload: Any fan of arcade shooters will know that it's time consuming to reload by shooting the gun away from the screen, and annoying losing your target.
Grenade Launcher: On the first level hit all enemies in the HEAD and when you reach the 1st Boss you will pick up a grenade launcher.
Note: This trick also works during the game!
Increase Life Stock: To increase the number of lives a player will have, rapidly push the start button while inserting coins.
Then, click on L 2 times, R 3 times, L once, R once and press Start before demo begins.
Show Score: L is the Left pistol trigger and R is the Right pistol trigger.