Come to think of it, there's LOTS of little details in DEus Ex that make that game rock hard. Just off the top of my head, the sheer amount of dialog availible if you keep talking to everyone is pretty good. Also, you can cause certain events to unfold differently in the story, like when Sandra Renton's being tossed up by her "boyfriend," normally, you walk up to him, talk to him, threaten him, and he leaves. Well, one day, I figured "screw that," whipped out my 10mm silenced, dealt him a triple tap to the head, and talked to Sandra..she acts all shocked and horrified that homeboy got blown away right in front of her!
You can also give her dad a pistol to help defend himself agains Jojo, (and if you hang out when Jojo comes downstairs and get in a fight with him, he'll help shoot the bastard)
Wow, what else.... in Hell's Kitchen, if you take the back way out of Smugglers, you'll see 2 NSF thugs roughing up some guy on the basketball courts. Wait long enough and they'll murder him on the spot. But if you shoot one of them, the other will execute the poor guy and fire on you. The only way I found to save them was to pop a teargas grenade and cap both the thugs, (the guy's real grateful, and gives you a bit of information)
Depending on what you do, Sandra Renton may or may not meet you at the gas station near Vandenburg....
Oh, and if your hacking skills are good (or if you use chests. ;-) ) you can read everyone's emails and figure out early a lot about what's going on....