Use this trick to easily reach a 999 kill streak and get a lot of badges for weapon upgrades. Area of effect damage weapons such as Acid Sprinklers, Flaming Compensator, and TNTeddy are most effective. Use the ammunition dropped by the dead OD to keep reloading. Instead of completing the objective, keep bouncing and killing the endless waves of OD. Play the "Getting The Band Back Together" mission, and progress to where you have to bounce on ten drums without touching the ground. If the enemies on the tower side kill you, the money and Overcharge will not respawn. Note: The money and Overcharge will only respawn if the enemies on the other side of the river kill you. Repeat this process as many times as desired. After crossing the river, start shooting your weapon to get the enemies attention so they kill you more quickly. Thus, you will have to cross the river to have enemies kill you in that area to make the money and Overcharge respawn again. After collecting the money and Overcharge a second time, there will be no nearby enemies to kill you. After collecting all of the money and Overcharge around that area, let the soldiers kill you to respawn back on top of the tower, along with the money and Overcharge on the ground. When you reach the top of the tower, the panic room will explode and send you falling to the ground with a bunch of money and Overcharge. This mission requires you to find Max's parents in a panic room on top of a tower.
Proceed through the main missions until you reach Act 1–9: "Max's Parents".