Have you found any easter eggs in DX? Stuff that serves no real purpose and was put there for no good reason?
I guess you'd call it an easter egg, I don't know what else you'd call it... but if you can get over the gate at UNATCO HQ after Battery Park, while Liberty Island isn't fully rendered, there is some stuff to be had, believe it or not.
The first time Liberty Island is off-limits, you've just destroyed the NSF generator. If you can get on top of the Statue's main room - rememeber where the NSF troop and mercenary were talking, the room with the four ways in, the three smoke grenades? There are two LAMs, each protecting one entrance. There's also an explosive barrel protecting another. If you go up from there, you'll run into a dead-end with a smoke grenade. All active.
The second and last time, it's after you meet Lebedev and killed him, or not. There's a crate up on the Statue, around where the three guys are pacing in front, containing a lockpick.
Taken from my own site (WWW link below) in the "Liberty Island off-limits spoils" article. The article also notes Manderley's safe (impossible to get at - it's behind the bookcase).