After purchasing flash, spray or weapons with dealers, you're free to kill them to grab your cash back as well as anything else left on the corpse.
Clear the game on Hardcore difficulty to unlock the Unleash the Fury. In this new mode you play through the main game as the Baseball Furies gang.
100% completion ... L, BACK, BLUE, DOWN, WHITE, RIGHT
Unlimited Health ... UP, YELLOW, L-CLICK, BACK, GREEN, WHITE
Unlimited Rage ... BLUE, RED, YELLOW, BACK, GREEN, LEFT
Unlimited Sprint ... DOWN, BLUE, LEFT, GREEN, L, BACK
Get Pipe ... BLACK, RED, BACK, UP, L, RIGHT
Get Machete ... L, GREEN, R, R, BACK, BLACK
Get Knife ... DOWN, DOWN, BACK, UP, UP, L-CLICK
Get Bat ... BLUE, BLACK, DOWN, DOWN, L, L
Get Outta Jail Move ... UP, BACK, GREEN, YELLOW, YELLOW, BLUE
Instant Win Level ... DOWN, BLUE, GREEN, BACK, R, LEFT
Clear the game once on Normal or higher difficulty and an arcade game at the hangout will be available (called 'The Warriors Armies Of The Night'). To actually play the machine though, you need to clear all the Flash Back levels.