Those who have finished Metal Gear Solid 4 know: Complete the game and you get access to a screen where you can enter passwords. We've shown you some of these before (here and here). Enter skynytktjp and get Mk.II scanning plug. Enter mgo2play and get SUBSISTENCE ACTION for the in-game iPod. So there you go.
『メタルギア ソリッド 4』の特殊アイテムをパスワードでゲットせよ [Famitsu]