You'd be forgiven for thinking this was for collecting all the camouflages, but it also includes all the costumes for use in Versus only as well.
Here is a complete list of all said camo's and costumes needed for this achievement.
First of all is the ones you start off with:
Black
Khaki
Navy Blue
White
Red
Yellow
Pink
Green
Water
Tree Bark
DPM
Comrade
G&J
NKD(Black)
NKD(Khaki)
NKD(N.Blu)
NKD(White)
NKD(Red)
NKD(Yelw)
NKD(Pink)
NKD(Grn)
NKD(Watr)
NKD(T.B)
NKD(DPM)
Naked
J.Fatigues
Then rest are obtained by either finding them on a certain level (this is made easier of you take someone with the Channeler ability as items appear on the map in the pause menu) or by simply clearing a mission, sometimes with a S rank. I'll list them in order that there are listed in the Mission Prep section
Sneaking - Complete MAIN OPS - Attack Chopper Battle: MI-24A.
Battle - Complete MAIN OPS - Peace Walker.
Battle W/H - Complete any OUTER OPS with a difficulty of S+ and above, this is a random drop so it may take a few attempts.
Leaf - S-Rank EXTRA OPS 014.
T.Stripe - MAIN OPS - Puruse Amanda, search around Banana Fruta De Oro.
Choco-Chip - S-Rank EXTRA OPS 045.
Auscam - MAIN OPS - Destroy the Barricade, search around Aldea Los Despiertos.
Squares - Search around Banana Fruta De Oro in EXTA OPS 030.
Splitter - Find the uniform on a crate in EXTRA OPS 059, get next to the crate, open your item menu highlight a box and drop it so you can climb on top of the box then the crate to get this one.
Snake - MAIN OPS - Travel to Cloud Forest, search Selva del la Leche: Hillside.
Neo-Moss - Use your codec near the first ghost in EXTRA OPS 062 until you hear "This is The End" then complete the mission. You will also get the Kuwabara, Kuwabara achievement as well getting this camo.
Stench - S-Rank EXTRA OPS 061.
Tigrex - S-Rank EXTRA OPS 123-124.
Rathalos - S-Rank EXTRA OPS 121-122.
Gear Rex - S-Rank EXTA OPS 125-126.
NKD(Leaf) - Received when you get the camo Leaf.
NKD(Tiger) - Received when you get the camo T.Stripe.
NKD(Choco) - Received when you get the camo Choco-Chip.
NKD(Ausy) - Received when you get the camo Auscam.
NKD(Sqrs) - Received when you get the camo Squares.
NKD(Split) - Received when you get the camo Splitter.
NKD(Snake) - Received when you get the camo Snake.
Tuxedo - Complete MAIN OPS - Peace Walker Battle 3.
Amanda - S-Rank EXTRA OPS 067 (Female only)
Miller - S-Rank EXTRA OPS 068 (Male only)
Bikini - After S-ranking EXTRA OPS 68, you will have to go back into the mission again wearing the swim trunks and it'll be on the wooden pier. (Female only)
Swim Trnks - After S-ranking EXTRA OPS 067, you will have to go back into the mission again and if Paz is in her swimsuit/underwear it'll be on the wooden pier. (Male only)
T-Shirt - Search EXTRA OPS 001, it's on the top floor.
R.Commando - Complete EXTRA OPS 037. (Versus only)
R.Soldier - Complete EXTRA OPS 024. (Versus only)
Scout - Complete EXTRA OPS 061. (Versus only)
Guard - Complete EXTRA OPS 038. (Versus only)
Commando - Complete EXTRA OPS 009. (Versus only)
M.POW - Complete EXTRA OPS 052. (Versus only)
F.POW - Complete EXTRA OPS 055. (Versus Only)
Patrolman - Complete EXTRA OPS 011. (Versus only)
Mechanic - Complete EXTRA OPS 066. (Versus only)
Escort - Complete EXTRA OPS 027. (Versus only)
Use this link if you need help unlocking certain EXTRA OPS after completing the main game
http://www.ign.com/boards/threads/metal-gear-solid-peace-wal...