Deus Ex actually came out in 2000. It was based on the original Unreal Tournament (used its game engine), which (UT) came out in 1999. The GOTY edition, which included multiplayer, came out in 2001. Here's a great resource on it - the Wikipedia page
Deus Ex has been for years and still is one of my favorite games. I have completed it over 10 times and I swear I still discover new bits of dialogue, secrets, and such. I have played it so much, that I don't feel I need to complete it honestly. I can beat it without cheats, but sometimes it's fun to play it with cheats, even certain ways. For example I'm currently playing as a Jedi (sort of) - god mode, no detection (invisible), and using the Dragon Tooth sword (basically a lightsaber). I have a fully tricked out assault gun with 20mmHE ammo (I keep using the Allammo cheat to keep it filled up) and a Plasma gun - actually this play-through is my first time using the weapon.
Did you know you can complete the first level without using a single inventory item? As long as you don't mind leaving Gunther in the cell, it's possible - and not all that hard - to get to the command center completely undected. Heck, I can run it, not worrying about being detected, and I'm pretty sure I can do it without getting hit - at least without getting killed. The first level has probably the most goodies (remember, Hells Kitchen is several maps) but you can get them after the leader surrenders. Just get on the island, hang a right, and go in the back way. If you're sneaking, there are only a few tight points.
I'll share a few of my favorite tricks with you...
When you start a new game, downgrade your pistol skills. Pistol use will actually cause your skill to go up on its own, without you spending skill points - up to advanced. You have to pay for mastery. So you can use the initial points (from Trained to Untrained) on other things.
When you've sent the distress signal, and report back to Paul, Paul is an invincible character. Whether Paul lives or dies depends on how you exit the 'Ton. If you're knocked out or if you exit through the front door, Paul lives. If you bail out the window, Paul dies. My favorite way of keeping him alive? First, before you talk to him, open his computer lab. Open the painting, and the code is 4321. Second, talk to him, and trigger the raid. Stick around long enough for MiB's to raid the apartment, then QUICKLY get in the computer lab, and hit the button - it's just to the left of the desk - to close the doors. Duck under the desk. Now get up, make yourself some coffee or whatever, wait for the sounds to die down. When they do, Paul will have killed the MiBs and the UNATCO troops outside. Turn on your light (F12) to see the switch to open the door. Run out in the hallway, begin to run down the stairs, but double back. Paul will clear the lobby for you. AFAIK he will not take care of the UNATCO agent on the balcony with the Sniper rifle or the four guys in the entry hallway. Take care of the sniper yourself, and either draw the other four out to be dealt with by Paul, or toss a few LAMs their way.
If Gilbert Renton has any hand in killing Jojo, Sandra Renton will not run away. Even if you give Mr Renton a tricked-out gun, it doesn't guarantee he will win the firefight. If Renton kills Jojo, Sandra will not run away. But the last time I did it, I gave Renton a tricked-out pistol, but he ran out of ammo, and rather than reload, he just ran. Jojo chased him, and I killed Jojo. Sandra still stayed. But I think if JC takes the first shot, Sandra still runs away. So I think all that has to happen is Renton has to take the first shot - then Jojo is all yours. I really don't think it matters if Sandra runs away or not, or even if Renton lives or dies, at this point. I just tend to get attached to those characters, and try to make things work out the best for them.
There are two medbot depots in the very first level. I swear, I did not know about them at all the first five times I played through. I only discovered them using the GHOST command (no-clip). The first is when you first get on the island, to the left, where the gas grenade is in a crate. Along the front of the bottom... box? ...is a UNATCO MEDICAL panel. Pointing at it should reveal a lockpick/destroy stat. Pretty sure you can pick it with just one lockpick. The second is behind the statue, also on ground level. If you are sneaking, when you are sneaking by the two NSF guys who admire Gunther (and will say so if you eavesdrop), you're going wide around them, between them and the road where the other two guys are, you'll come to another box/crate like thing where you'll consider yourself safe. Pretty sure it's that one. Same thing, UNATCO MEDICAL panel on one side. That one has three medbots in it, not sure how many the first one has. Once you open one or the other, of course you can get free health refills just by returning to that point. If you opened the first one, you can theoretically install the aug you find at the top of the statue, though at that point it's just easier to go into UNATCO HQ and do it in Jaime's office.
The AI in Deus Ex was pretty good, but it had a couple flaws. If you were behind a barrel, enemies would not see you if the barrel was between you and them. They would not suspect a barrel being pushed in their direction, either. Good example any DX player can relate to, the dock in the first level, the one Harley Filben's at. There's an NSF Terrorist walking around the crates and a Mercenary standing still. If you go around the left side pushing a barrel, you can actually get by undetected both times. You can get to Filben, heck you can even get the medkit on the other side, and back onto the island without alerting either guy.
And last but not least, if you don't mind blood on your hands, you can lure bad guys to the walking bot in the first mission. Paul will still blame you for the deaths (this matters none) but you don't have to kill them, and can loot their bodies for ammo. Just run around in front of an NSF Terrorist to get his attention, then book it back to the dock. He'll give chase, and as soon as one of his bullets hits either Paul or the robot, they're dead. If they hit the robot, the robot alone will return fire. If they hit Paul, I'm pretty sure both Paul and the robot will return fire, and Paul carries a plasma gun. Paul is invincible, so he won't die. You can get half the bad guys to do this, with either bot. Though it's more dangerous, you can even get the NSF's bot to chase you, and get gunned down on either side. (If you do that, prepare to do a lot of weaving, jumping, and getting behind objects... but don't get too far ahead, or the NSF's bot will just give up.) Take some damage, but don't get killed. If you get rid of the NSF's bot this way, consider shelling out a lockpick to get into the medical bot depot right there at the beginning.
Oh, and I didn't care for DX multiplayer. I play it exclusively offline.