At the main menu, select "Exclusive Content" and enter "735S653J" to get extra money for equipment in single-player mode, silver weapons in multiplayer mode, and an exclusive weapon for the first two chapters.
Jumping and switching weapons while in mid-air is an excellent way to help keep your current speed and momentum, especially if you find yourself being chased by someone in a multiplayer game and are low or out of ammo for your current weapon.
AsThomas, equip a Volcano gun or better weapon in good condition. Wear Barnsby until Thomas can use Concentration mode, then fire all 12 shots directly into him. The game may glitch and he may die without need of the quick draw sequence. You will then view the ending.