In Metal Gear Solid:Peace Walker for the PSP, there is a laundry list of in-game t-shirts you can unlock with some passcodes. You’ll need a Playstation Network account to access these however.
From the title screen, go to Extras > Network > Enter Passcode and put in the following codes:
Black shirt with Big Boss text – 2000016032758
Black shirt with Peace Walker text – 2000016032390
Black shirt with white Peace Walker logo – 2000016038415
Blue shirt with MSF logo – 2000016032635
Gray shirt with coffee cup design – 2000016036022
Gray shirt with MSF logo – 2000016032567
Gray shirt with MSF logo #2 – 2000016032574
Gray shirt snake design on back – 2000016032338
Green shirt with snake design – 2000016035902
Red Big Boss face a la Che shirt – 2000016537833
Tan shirt plain – 2000016038576
White shirt with Big Boss face – 2000016756791
White shirt with Big Boss text – 2000016032680
White shirt with UNIQLO logo – 2000016035933
