Cheat Mode
I recently stumble on this little code, which many might find usefull when going around the game. It permits all that other codes don't, mainly, all biomods or a precise mod at a precise level, weapon generation and a few other usefull things as well. To use this, I suggest making a copy of your DX2UI.ini file, which can be found in the game's /System folder. The original should be modifed like so:

Find the tag named "[DebugMenu]" and modify the data to match this:

[DebugMenu]
Active=ACTIVE
Type=Menu
Placement_X=RIGHT
Placement_Y=BOTTOM
PauseGame=False
AutoSizeWidth=True
AutoSizeHeight=True
TextColor_A=24
Color_Normal_A=0
TextShadowColor_A=0
SelectedColor_A=48
UnselectedColor_A=24
Font=font8
MenuDefinitionFile=DX2Menu.ini
ListenForMouseClicks=True
InputLayerName=DebugMenu

Once done, save this and load the game. You'll notice a menu in the screen on the lower right. To use it, load or start a game, press escape to bring down the HUD, and scroll the menu with your mouse.

Once your done, you can save your game, exit, switch back to your old DX2UI.ini and resume gameplay, to get rid of the debug menu.

Invulnerable, aiming accuracy, more ammo
First off, in the pc version, you cannot logically do anything with the user.ini that others try to claim credit for finding. It just can't be done. THERE'S NO CHEAT CONSOLE by trying to use T__d=Talk! Secondly, since there's no console, any cheats posted are most likely copied from the original Deus Ex listings.

I have found the only cheats at present are the following, just alter the Default ini by making the numbers on each line ending just like the following:

[Difficulty]
; AI Damage multiplier - damage AIs take from player
Difficulty_AI_Damage_Easy__d=4.25
Difficulty_AI_Damage_Normal__d=4.0
Difficulty_AI_Damage_Hard__d=4.75
Difficulty_AI_Damage_Real__d=4.5
;
; Player Damage multiplier - damage player takes from AIs
Difficulty_Player_Damage_Easy__d=0.0
Difficulty_Player_Damage_Normal__d=0.0
Difficulty_Player_Damage_Hard__d=0.0
Difficulty_Player_Damage_Real__d=0.0
;
; 1.0 = base accuracy, 0.0 = wild, 2.0 = as accurate as it gets (not 100% perfect)
Difficulty_Accuracy_Easy__d=2.0
Difficulty_Accuracy_Normal__d=2.0
Difficulty_Accuracy_Hard__d=2.0
Difficulty_Accuracy_Real__d=2.0
;
; Ammo multiplier for difficulty levels
Difficulty_Ammo_Mult_Easy__d=2.0
Difficulty_Ammo_Mult_Normal__d=2.0
Difficulty_Ammo_Mult_Hard__d=2.0
Difficulty_Ammo_Mult_Real__d=2.0