Resident Evil: Code Veronica

In order to get a sexy biker costume for Claire Redfeild in battle mode, you must complete battle mode as Claire Redfeild.
At the player select screen in battle mode there will be two Claire Redfeilds to chose from.
The oringinal and the biker costume.

To play as Wesker in Battle mode, you must comple battle mode as Chris Redfeild.
Wesker will then be available on the player select screen in battle mode.
Wesker only has a knife for self defence.

To have Steve Burnside in Battle Mode you must collect a golden Luger.
It is on Disc 2 where Chris Redfield is about to fly of to Antartica, instead go in the room near it with a draw puzzle.
It is in there, but you must work out the puzzle to collect it, hint: Look for clues.

Battle mode
Successfully complete the game on any difficulty setting.
Then, battle mode will automatically be saved to the VMU and selectable at the main menu.
Note: To play battle mode in first person view, pick up Ashford's sniper rifle once he drops it on Disc 2.