There are 3 possble endings in the game which are unlocked depending on what you opted to do during the game.

Unlock Ending A:
Merge with the Helios AI.

Unlock Ending B:
Agree to Morgan Everett's proposal to join the Illuminati and killing Bob Page.

Unlock Ending C:
Do as Tracer Tong says and destroy the world's communications.

Enable Cheat Mode:
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.

Combat Strength:
AugCombat

Microfibral Muscle:
AugMuscle

Ballistic Shield:
AugBallistic

Energy Shield:
AugShield:

Cloak:
AugCloak

Radar Transparency:
AugRadarTrans

Synthetic Heart:
AugHeartlung

Power Recirculator
AugPower

Swim better:
AugAqualung

Increased healing rate:
AugHealing

Environmental Resistance:
AugEnviro

EMP Shield
AugEMP

Targeting:
AugTarget

Vision Enhancement:
AugVision

Aggressive Defense System:
AugDefense

Spy Drone:
AugDrone

Run silently:
AugStealth

Run faster:
AugSpeed

10,000 credits
allcredits

All basic augmentations:
allaugs

All images:
allimages

All skill points:
allskillpoints

allskills:
Master in all skills

All weapons:
allweapons

Disable enemy AI:
players only

Disable flight and no clipping modes:
walk

Display ending quotes:
quotes

Enable EMP field:
iamwarren

Flight mode enabled:
fly

Full ammunition:
allammo

Full energy:
allenergy

Full health:
allhealth

God mode:
god

Hidden fourth ending:
danceparty

Hidden menu:
legend

Kill current target:
tantalus

Matrix mode
thereisnospoon

More energy:
set deusex.jcdentonmale energy 10000

No clipping mode:
ghost

Programmer message:
huthut

Programmer message:
bighead

Set game speed:
slomo (number)

Set view angle:
fov (1-360)

Spawn indicated:
item summon (item name)

Spawn number of items:
spawnmass (number) (item name)

Third party view disabled:
behindview 0

Third party view enabled:
behindview 1

Toggle invisibility:
invisible (0 or 1)

View character:
cheatview (character name):

Breathe underwater:
amphibious

Set jumping ability:
setjumpz (height)

Kill indicated character types:
killall (character type)

Kill all pawns:
killpawns

Remove indicated nanokey:
removenanokey (nanokey number)

Get description of nanokey:
givenanokey (nanokey number)

Display refresh rates:
togglewinstats

Display window color dialog:
showrgbdialog

Damage all body parts:
damageall (amount)

Opens/hacks target:
opensesame