This trick will help you gain money to max out and buy all the weapons. In any chapter, collect as much gold, items, ammunition, and treasure you can find. When you are satisfied, pause game play and quit the game. Save the game when prompted. Restart any desired chapter. The "Shop" menu will appear before the start of any chapter. Notice that all the gold, treasure, weapons, and ammunition from your previous saved game are still in your inventory. From there, you can sell anything you want to gain some fast cash. This glitch can be done repeatedly, on any chapter.
Go through a chapter, collecting as many hand grenades as possible. Then, start Co-op mode with a friend, system link, or over the Internet. Give your partner all of your grenades and have them exit the game. After they leave, your AI partner will still have all of the grenades. Make sure you request them back. While you do this, your friend that left can sell the ones he took with him. You can have up to five in each slot, and they sell for 250 gold each. You will gain 11,322 gold each time you do this (if you have all your slots full). This is also a good way to stock up on ammunition.
Start Chapter 2-1 under any difficulty setting with a friend via the Internet. Note: You must have eggs to do this trick. Begin your game with your partner. Have whoever has the eggs drops out of the game, leaving all the eggs to the AI character. Have the other person then request all of the eggs from the AI character and complete the level, making sure that the game saves. Then, go back into the game with your partner at the same level, making sure that you have the eggs in every inventory slot. Then, drop out, leaving all the eggs to the AI. Have your partner request all the eggs, then complete the level. You can repeat this as many times as desired. The eggs will multiply each time you do this and you can sell them for 2,000 gold. This is a way to receive unlimited amounts of money to buy whatever you need.
