Complete and save the game with any ranking and Battle Mode will be unlocked (selectable through the main menu).
To play Battle mode in first person view, pick up Alexia's sniper rifle once she drops it towards the end of Disc 1. (In the Japanese version of the game, pick up Alfred Ashford's sniper rifle once he drops it on Disc 2.)
Get the Gold Lugers from the basement office in Disc 2. The correct combination is red, green, blue, and brown. You can also unlock Steve Burnside by performing well with the original Chris in Battle mode.
Complete the game with Chris Redfield in Battle mode.
Complete the game with the original Claire in Battle mode.
Get an A ranking with Steve Burnside, Albert Wesker, Chris and both versions of Claire in Battle mode to unlock the linear launcher. It will automatically appear in your inventory during the next Battle mode game.
Get an A ranking in the normal game. There's a well written FAQ on how to do this, but in short: complete the game without saving, without using first aid sprays, and without retries. You must also save Steve from the Luger quickly, give the Medicine to your jailer Rodrigo, and complete the game in less than 4 hours and 30 minutes. After all this, when you begin a new game, the rocket launcher will appear in the first item box you find.
Japanese version: - Up, Up, Down, Down, Left, Right, R
european version: - Up, Up, Down, Down, Left, Left, Right R
submitted by lloyd