Extra Hit Points
In the Octopus stage, you can shoot the crab for some bonus hit points. In any of the stuffed toy stages, you can repeatedly shoot the glass that shows your target and get many bonus hit points. In most of the criminal stages, you can shoot out the windows of cars or buildings and get many extra hit points. If you shoot out a window when a criminal pops up, you can also get more than 100% accuracy and get more points. In some of the protecting Dr. Don and Dr. Dan stages, you can shoot them and get hits for shooting them.

Extra Hit Points Method 2
In the criminal level where you are moving down the corridor of a hotel. If you shoot the lights on the ceiling you will gain extra hit points thus boosting you score.

Find the Map
In quest mode, start a new game and go down until you see a raft. Run over it to get the map.

Power Shotgun and Power Machine Gun
The Power Shotgun and Power Machine Gun in Quest Mode are found in the last level. You go to the second town (The town without the inn) and head south along the eastern edge of trees. About half way between that town and the small hut, there will be a secret entrance into the forest. You must navigate through the forest maze and get into the large pond on the other side. Once you get there, head just north of the uppermost ducks in the pond and near the center. Search around and you should find the Power Shotgun. Then, travel south through the pond and you should find the Power Machine Gun. These two items are just the Shotgun and Machine Gun that can be used an infinite number of times.

NOTE: To use the Power Shotgun, you must have a dexterity of at least 40. To use the Power Machine Gun, you must have a dexterity of at least 60.