Halo 3: ODST - Insane Marine On Uplift Reserve
On the mission Uplift Reserve near the end of the mission, there are two marines talking to each other and one of them is going insane. This is pretty much like the insane marines from Halo 1 and Halo 3. The only difference is that this one is a lot more funny than the ones in Halo 1 and Halo 3. This marine may or may not be secret. It depends on how you look at it. The marine will always say the same things no matter what difficulty you play on.