Interesting debugging tool for those that are bored.
DEBUG / BURGER MENU
The Debug Menu allows you to manipulate the game (no health regen, infinite power, infinite ammo, AI options, UI options) and has a "Shop" feature, which lets you spawn yourself augmentations, money, weapons, weapon mods and other in-game items, as well as tons of debug options which you probably should leave alone.
You access this via the Pause menu.
It also comes with a "Map Selection Window", which lets you pick which map to load. The list also has some "unused" maps like the E3 Demo and GamesCom, along with "Zoo" maps (which are usually maps with all NPCs and items so you can quickly test things), although the only one I could load was the "E3 Demo" one, and I think it's identical to the retail Hengsha map, except without NPCs. So I'm guessing the maps themselves aren't actually included.
You access this via the Main menu.
1) Navigate into ..\Steam\steamapps\common\deus ex - human revolution\ (finding these folders depend on where you have Steam installed) and make a backup of patch0.000 though you can have Steam redownload it by doing verify integrity if you want the original file back.
2) Unpack the download into the same folder, so you'll have a "new", modded patch0.000 file. If you don't need a backup, over-write the existing file.
Only works with game version 1.1.622.0
(Mirroring in case thread gets removed)