How do you unlock the Chicago Typewriter in Resident Evil 4?
Solution 1:
In the GameCube version, it is available for 1,000,000₧ after beating the Assignment Ada minigame. In all other versions, beating Separate Ways will unlock this gun for the main game for the same price, while beating Assignment Ada will unlock it for Separate Ways, where it costs 300,000₧.
Source http://residentevil.wikia.com/wiki/Chicago_Typewriter