Gears of War 3

[twistedsymphony]

Both Gears1 and Gears2 were re-released as 2-disc editions, where the 2nd disc held the DLC expansions.

http://collectorsedition.org/game-db...ition-360-ntsc
http://collectorsedition.org/game-db...ition-360-ntsc

it's possible that the 6th slot is for a potential gears of war 3 expansion disc.

of course the CE for each game also had 2 discs, with the 2nd disc housing behind the scenes content.