Unlock All Weapons & Professional Difficulty
     Complete these tasks to unlock the following.

Unlockable:                   How to Unlock:

All Primary Weapons           Complete the game on either "Recruit" 
                              or "Contractor" difficulties.

Professional Difficulty       Complete the game on either "Recruit" 
                              or "Contractor" difficulties.

All Remaining Weapons 
(Secondary & Special)         Complete the game on "Professional" 
                              difficulty.