During game play, hit the talk key (usually the T button) delete Say, and then type
Set DeusEx.JCDentonMale bCheatsEnabled True
Now hit return. You just enabled the cheat mode.

After you enable the cheat mode, hit the talk key, delete Say, and type in allcredits.

After you enable the cheat mode, hit the talk key, delete Say, and type in allaugs.

Third Person View
Press the Talk button and erase 'Say' then enter:
behindview 1
To return to First Person View simply press the Talk button and erase 'Say then enter:
behindview 0
Enable Cheats
To enable cheats, make a backup copy of a game file. Once this is done, open 'user.ini' in a text editor. It can be found in the deusex/system directory. Now assign the T key (upper and lower case) to 'talk.' Change all entries for the T key in the file, then save it and exit. Launch the game. During gameplay, press T and the computer will display the prompt 'Say.' Delete this and enter instead 'set DeusEx.JCDentonMale bCheatsEnabled True' to enable cheat mode. Then to enter a cheat, press T again and type away.
Cheat List
After enabling cheats and pressing 'T' to bring up the cheat menu.
allcredits: 10,000 credits
augadd (augmentation name): Add indicated augmentation
Augmentation Names:
AugCombat: Combat Strength
AugMuscle: Microfibral Muscle
AugBallistic: Ballistic Shield
AugShield: Energy Shield
AugCloak: Cloak
AugRadarTrans: Radar Transparency
AugHeartlung: Synthetic Heart
AugPower: Power Recirculator
AugAqualung: Swim better
AugHealing: Increased healing rate
AugEnviro: Environmental resistance
AugEMP: EMP Shield
AugTarget: Targeting
AugVision: Vision Enhancement
AugDefense: Aggressive Defense System
AugDrone: Spy Drone
AugStealth: Run silently
AugSpeed: Run faster
allaugs: All basic augmentations
allimages: All images
allskillpoints: All skill points
allskills: Master in all skills
allweapons: All weapons
players only: Disable enemy AI
walk: Disable flight and no clipping modes
quotes: Display ending quotes
iamwarren: Enable EMP field
fly: Flight mode enabled
allammo: Full ammunition
allenergy: Full energy
allhealth: Full health
god: God mode
danceparty: Hidden fourth ending
legend:Hidden menu
tantalus: Kill current target
open (level name): Level and FMV sequence select
Level names
00_Training
00_TrainingCombat
00_TrainingFinal
01_NYC_UNATCOHQ
01_NYC_UNATCOIsland
02_NYC_Bar
02_NYC_BatteryPark
02_NYC_FreeClinic
02_NYC_Hotel
02_NYC_Smug
02_NYC_Street
02_NYC_Underground
02_NYC_Warehouse
03_NYC_747
03_NYC_Airfield
03_NYC_AirfieldHeliBase
03_NYC_BatteryPark
03_NYC_BrooklynBridgeStation
03_NYC_Hangar
03_NYC_MolePeople
03_NYC_UNATCOHQ
03_NYC_UNATCOIsland
04_NYC_Bar
04_NYC_BatteryPark
04_NYC_Hotel
04_NYC_NSFHQ
04_NYC_Smug
04_NYC_Street
04_NYC_UNATCOHQ
04_NYC_UNATCOIsland
04_NYC_Underground
05_NYC_UNATCOHQ
05_NYC_UNATCOIsland
05_NYC_UNATCOMJ12lab
06_HongKong_Helibase
06_HongKong_MJ12lab
06_HongKong_Storage
06_HongKong_TongBase
06_HongKong_VersaLife
06_HongKong_WanChai_Canal
06_HongKong_WanChai_Garage
06_HongKong_WanChai_Market
06_HongKong_WanChai_Street
06_HongKong_WanChai_Underworld
08_NYC_Bar
08_NYC_FreeClinic
08_NYC_Hotel
08_NYC_Smug
08_NYC_Street
08_NYC_Underground
09_NYC_Dockyard
09_NYC_Graveyard
09_NYC_Ship
09_NYC_ShipBelow
09_NYC_ShipFan
10_Paris_Catacombs
10_Paris_Catacombs_Tunnels
10_Paris_Chateau
10_Paris_Club
10_Paris_Metro
11_Paris_Cathedral
11_Paris_Everett
11_Paris_Underground
12_Vandenberg_Cmd
12_Vandenberg_Computer
12_Vandenberg_Gas
12_Vandenberg_Tunnels
14_OceanLab_Lab
14_Oceanlab_Silo
14_OceanLab_UC
14_Vandenberg_Sub
15_Area51_Bunker
15_Area51_Entrance
15_Area51_Final
15_Area51_Page
FMV names
00_Intro
99_Endgame1
99_Endgame2
99_Endgame3
99_Endgame4
thereisnospoon : Matrix mode
set deusex.jcdentonmale energy 10000: More energy
ghost: No clipping mode
huthut: Programmer message
bighead: Programmer message
slomo (number): Set game speed
fov (1-360): Set view angle
item summon (item name): Spawn indicated
spawnmass (number) (item name): Spawn number of items
behindview 0: Third party view disabled
behindview 1: Third party view enabled
invisible (0 or 1): Toggle invisibility
cheatview (character name): View character
amphibious: Breathe underwater
setjumpz (height): Set jumping ability
killall (character type): Kill indicated character types
killpawns: Kill all pawns
removenanokey (nanokey number): Remove indicated nanokey
givenanokey (nanokey number): Get description of nanokey
togglewinstats: Display refresh rates
showrgbdialog: Display window color dialog
damagepart (part number), (amount): Damage indicated part
Part numbers
0: Head
1: Torso
2: Left arm
3: Right arm
4: Left leg
5: Right leg
damageall (amount): Damage all body parts
opensesame: Opens/hacks target
Submitted by special thanks to olanmills
Item Names
Use these item names where (item) is indicated in the cheat list:
acousticsensor
adaptivearmor
alexjacobson
ammo10mm
ammo20mm
ammo3006
ammodart
ammodartflare
ammodartpoison
ammonapalm
ammoplasma
ammorockets
ammorocketwp
ammosabot
annanavarre
atm
augballistic
augcloak
augdatalink
augemp
augenviro
augiff
augshield
augstealth
augtarget
autoturret
babykarkian
ballisticarmor
bartender
basketball
binoculars
boatperson
bobpage
boneskull
bookclosed
bookopen
bumfemale
bummale
bummale2
bummale3
businessman1
businessman2
businessman3
businesswoman1
butler
button
candybar
cat
ceilingfan
chef
childmale
childmale2
cigarettemachine
cigarettes
cleanerbot
computerpersonal
computerpublic
computersecurity
cop
crateunbreakablelarge
crateunbreakablemed
crateunbreakablesmall
credits
datacube
dentonclone
doberman
doctor
fan1
fan2
faucet
female1
female2
female3
female4
fireextinguisher
fish
flagpole
flare
flowers
fly
garysavage
gordonquick
gray
greasel
harleyfilben
hazmatsuit
hkbuddha
hkhangingpig
hkmilitary
hooker1
hooker2
jaimereyes
jcdentonmale
jock
joegreene
jojofine
josephmanderley
junkiefemale
junkiemale
karkian
karkianbaby
keypad1
keypad2
keypad3
lamp1
lamp2
lamp3
lifesupportbase
liquor40oz
liquorbottle
lockpick
lowerclassfemale
lowerclassmale
lowerclassmale2
luciusdebeers
maid
male1
male2
male3
male4
maxchen
mechanic
medicalbot
medkit
mib
microscope
militarybot
minisub
mj12commando
mj12troop
morgoneverett
multitool
mutt
newspaper
newspaperopen
nicoletteduclare
nurse
pauldenton
pigeon
pillow
pinballmachine
poolball
rachelmead
rat
rebreather
repairbot
retinalscanner
riotcop
roadblock
salior
sarahmead
seagull
secretservice
securitybot2
securitybot3
securitybot4
showerfaucet
showerhead
sodacan
soldier
soyfood
spiderbot
spiderbot2
terrorist
tiffanysavage
toilet
tracertong
unatcotroop
van
vendingmachine
vialambrosia
vialcrack
waltonsimons
watercooler
waterfountain
weaponassaultgun
weaponassaultshotgun
weaponbaton
weaponcombatknife
weaponcrowbar
weaponempgrenade
weaponflamethrower
weapongasgrenade
weapongepgun
weaponhideagun
weaponlam
weaponlaw
weaponminicrossbow
weaponmodaccuracy
weaponmodclip
weaponmodlaser
weaponmodrange
weaponmodrecoil
weaponmodreload
weaponmodscope
weaponmodsilencer
weaponnanosword
weaponnanovirusgrenade
weaponpeppergun
weaponpistol
weaponplasmarifle
weaponprod
weaponrifle
weaponsawedoffshotgun
weaponshuriken
weaponstealthpistol
weaponsword
whchairovaloffice
whpiano
whredcouch
wib
winebottle
Glitch: Unlimited Experience
On the Ocean Lab Silo level where you go to leave with Jock, Dr. Savage should be on the rooftop waiting for you. He will give you a Augmentation Upgrade Cannister and you will recieve 500 experience points. Now if your inventory is full when you go to recieve the Aug upgrade Cannister you'll tell him you cant carry it and recieve the 500 points anyway. But if you keep talking to him while you still have a full inventory each time the conversation ends you will recieve another 500 Experience Points! Do this as often as you like till your ready to proceed in which then discard something from your inventory briefly talk to Savage one last time do your Aug Upgrade get your discarded item back and your ready to go!!!!
Submitted by Smaf
Hint - Multitool Hack
This was done with the latest patch 1112fm. I'm not sure if this works with any other versions of the game. Take out a multitool/lockpick, and start picking away at whatever you choose. (Keypads, locks, whatever.) Now just enter the menu/inventory screen and cruise around for a while. I'd say give it 30 seconds tops for a 100% lock.
Exit the screen and walla! You just unlocked whatever it is you decided to.. with one lockpick/multitool! This works with anything that needs unlocking and negates the need to upgrade the skills involved with lockpicking/multitooling.
Submitted by dennedawg

After you enable the cheat mode, hit the talk key, delete Say, and type in walk.

After you enable the cheat mode, hit the talk key, delete Say, and type in iamwarren.

After you enable the cheat mode, hit the talk key, delete Say, and type in behindview0.

After you enable the cheat mode, hit the talk key, delete Say, and type in fly. You will now be able to float around the area.

After you enable the cheat mode, hit the talk key, delete Say, and type in allweapons.

After you enable the cheat mode, hit the talk key, delete Say, and type in god.

After you enable the cheat mode, hit the talk key, delete Say, and type in legend.

At the end of the sub base mission, if you saved Savage's daughter he will give you 500 skill points and an Aug Canister.
Before you talk to him, make sure your inventory is completely full. When you talk to him, you will get 500 points, but you'll get the message to drop an item. Just talk to him again, and you will still get 500 points. Repeat this as much as you want to max out all your skills.
Note: This does not work on the patched version of the game.

After you enable the cheat mode, hit the talk key, delete Say, and type invisible. Type the cheat again to disable it.

After you enable the cheat mode, hit the talk key, delete Say, and type in tantalus.
This doesn't work on targets that can't die such as scientists in the training level.

After you enable the cheat mode, hit the talk key, delete Say, and type in allskillpoints.

While in cheats mode hit 't' and delete the words say and type 'playersonly' but one thing you can only fire once and can't use doors and movers (useful if you want to get away from an enemy)

After you enable the cheat mode, hit the talk key, delete Say, and type in allammo.

After you enable the cheat mode, hit the talk key, delete Say, and type in allenergy.

After you enable the cheat mode, hit the talk key, delete Say, and type in allhealth.

Most of the Unreal Tournament cheats work and UT cheat mods..
Step one: in order to enter these codes:
First turn on Cheat mode:
Step two: replace 'say' with the following cheats
*Suicide - (Both UT and DEUS EX) Very quick death.. best if used while playing around with a dead-end Map (that you're testing..)
*Killpawns (both UT and DEUS EX) kills everything that moves.. even the 'unkillable' die but you (well more like they are removed) only try this if you are in one of those mission where you don't need to talk to anybody to move on..
*slomo # (both UT and DEUS EX) slows or speeds up gameplay by the amount (0.01 Slow to 10 fast)
*Summon [actorname] (both UT and Deus EX) a weaker version of the famous Spawnmass (ex. Summon DeusEX.Jcdentonmale or Summon LAM [becafeful while summon a LAM becasue you auto throw it])
*Allskills (only Dues EX) gives you all the skills and upgrades them to max and lots of skill points

After you enable the cheat mode, hit the talk key, delete Say, and type in spawnmass.

After you enable the cheat mode, hit the talk key, delete Say, and type in behind view 1.

After you enable the cheat mode, hit the talk key, delete Say, and type in allimages.

After you enable the cheat mode, hit the talk key, delete Say, and type in opensesame.

After you enable the cheat mode, hit the talk key, delete Say, and type in ghost.