This wonderful mod (and the modding tools which are still being written) has been built by the Something Awful Forums regular gibbed. What it does is in the thread name, but let me elaborate.
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.
The mod used to disable the intro logos, but now that the game's been patched so you can skip them, there's no need for that anymore.
DOWNLOAD (Vanilla DX:HR):
map-select+debug-menu_1.3.643.1.7z (directly from gibbed)
map-select+debug-menu_1.3.643.1.7z (my mirror)
WILL ONLY WORK WITH GAME VERSIONS 1.3.643.1 and 1.4.651.0
Whenever there will be a patch, the mod will have to be "repackaged".
Installation: (Vanilla DX:HR)
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 patch2.000 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 patch2.000 file. If you don't need a backup, over-write the existing file.
DOWNLOAD (DX:HR Director's Cut):
modhook+map-select+debug-menu_126.96.36.199_patch1.7z (directly from gibbed)
WILL ONLY WORK WITH GAME VERSION 188.8.131.52 (INGAME: 184.108.40.206)
Installation: (DX:HR Director's Cut)
1) Navigate into ..\Steam\SteamApps\common\Deus Ex Human Revolution Director's Cut\ (finding these folders depend on where you have Steam installed) and make a backup of DFEngine.dll 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. The Director's Cut version of the mod uses a new "mod-hook" since there hasn't been a patch file yet to alter.
Note: You need an application like http://www.rarlab.com/rar_archiver.htm or http://www.7-zip.org/ to actually unpack it, since the packed download is a bit over 8 megabytes and the unpacked version is almost 30!