Successfully complete a level 3 weapon challenge at the PMC Villa with Fiona to unlock the corresponding costume in order for the indicated character. There are a total of three costumes for each character. The Pistol challenge is the easiest to complete. The Emplacement Weapons and Grenade Launcher challenges are about even; however, Emplacement Weapons is slightly more difficult when you have to shoot the flying cars. The Sniper challenge is the most difficult to complete.