Champion's Jacket
Inside the "Hostile Zone" at the Fortune City Arena

Chuck Greene's Outfit
Have a previous save from Dead Rising 2

Dealer Outfit
Find it in the managers office where you save Lenny Mooney in the Yucatan Casino

Ninja Boots
Found in The Mans Sport in Uranus Zone

Ninja Hood
Find it in the secret sniper spot in Royal Flush Plaza

Ninja Mask
Is it near the nightclub in Yucatan. At the end of the hall full of zombies, there is a door on the left, and a desk on the right. The mask is behind the desk.

Ninja Outfit
Get the achievement "Elite Killer" which is to kill 1337 zombies.

Protoman Blaster and Shield
Finish the game with an S Ending (Beat Overtime)

Protoman Boots
Found inside the Ultimate Playhouse store in Palisades Mall

Protoman Helmet
Save Jack in the "Welcome to the Family" case, then beat him in strip poker in the "Ante Up" case.

ProtoMan Suit
Get Bronze or better on all challenges in Sandbox Mode.

Psycho Body
Defeat the psychopath Carl

Psycho Boots
Early in the game, once you get Rebecca to the security room, the boots are inside

Psycho Mask It is in the wedding chapel where you fight Randy
Psychopath Hair
Wait the midnight Time Share movie in Paradise Platinum Screens

Soldier Body
Defeat Sgt Boykins

Soldier Boots
It is in a small room is south plaza on a cardboard box

Soldier Face Paint
Find it in Shanks in Palisades Mall

Soldier Goggles
Buy them in the Silver Strip pawn shop for $2,000,000

Sports Fan Boots
It is in the Sportrance store in Royal Flush

Sports Fan Clothes
On a rack on the first floor of KokoNutz in Palisades Mall

Sports Fan Face Paint
Find it on the awning at Americana Casino

Sports Fan Helmet
Hidden in the back room of Hot Excitorama

Tattered Clothes
Get the achievement "Party Time" which is to get a survivor drunk

Willamette Mall Uniform
Visit 10 Maintenance rooms (this also unlocks the Maintaining the City achievement)