Successfully complete the individual Silent Scope games to unlock bonus options for each, such as "Additional Health" and other assorted effects (wanna make all the pedestrians look like enemies for extra challenge?).

Complete all Silent Scope EX missions to unlock Professional Mode, with no crosshairs to show where enemies are.

Complete all Silent Scope EX missions to unlock Continuous Mission, where you play all missions with one life.

During the EX missions, where to man with the afro in the helicopter tries to kill you, wait until he flys off and turns around. Instead of trying to get lucky and shoot the afro guy, shoot the teddy bear that is painted on the helicopter.

Complete Continuous Mission to see the Prince of Rose and the Phantom kiss.