Metal Gear Solid 4. Inputting the access codes in the 'Extras' menu gives players two new weapons: Thor .45-70 large-caliber hand rifle and The Boss' Patriot from Metal Gear Solid 3. Here are the two codes, respectively: tshsniammr and pkhhnwhsjt.
In addition to the new codes, there's also new music for the in-game iPod titled "Battle." It's a track from the Plant Chapter in MGS2. It seems Konami is really cranking up the fan service ... and we like it!