I tried to go through nonlethaly on my first playthrough.
It wasn't the last time I died, but it was the first time I died a whole lot.
(wasn't till SWAT4 coop that I realized that sometimes killing bad guys is OK)
That game (SWAT4) is bloody good fun on a non-lethal playthrough if you know what you're doing and you use your wedges and taser well. Wedges are REALLY important if you want to make sure no civilians or suspects escape the scene. Always secure all other entrances aside from the one you're using to get inside, and if you encounter an intersection, leave one or both of your elements behind to cover it or wedge it until you've secured the first area and are ready to come back. Usually it won't be that simple though and occasionally you'll have to leave an area unsecured in order to finish the mission.
Its only okay to shoot a guy if you give him a warning and he doesn't put down his gun immediately (within one or two seconds of you or a teammate issuing the order), or he opens fire at all. Basically a criminal is always putting someone in danger by firing a weapon, and you're always allowed to take him down if he does so, even if he isn't shooting specifically at a person. The idea is that the bullet he fired from his gun could have hurt someone, even if he wasn't aiming at you, and that you have the right to stop him from using that weapon via any means in order to ensure the safety of the lives of your team, bystanders and the suspects themselves.
If you bust into a room and headshot everyone without giving them a chance to surrender, then you're going to lose a lot of points.
If you're playing on hard, always take light armour. Speed is more important, and you'll stand a much better chance of surviving if you can take cover quickly.
I got up to the last level nonlethaly, but only using the solo bots as bullet fodder. I must have missed some cue because I swear the suspects would occasionally lower their guns past their knees before instantly, as far as I could tell, opening fire. Which is fine when blue 2 soaks the hit, giving me time to fire the 3-5 beanbags necessary to
break their arms finally get them to put the gun down for reals.
When I played coop, though, it was just three of us and nobody wants to sit out the rest of the mission. I usually carried armor-piercing rounds, a tazer, one door wedge, and the rest flashbangs. (Armor-piercing actually does less damage, so they have a good chance to survive, and it works better against the dozens of fully armored terrorists that our 3-person team had to face). We did still shout - nobody wanted a bad score - but if they shook off the flashbangs, we didn't give them much time to comply. There was no time to take cover.
I think this is sort of thread-relevant. It's one of the few coop games where it really, really sucks to die. The realism and the amount your friends are counting on you really increase the impact.
The last time I died though was in Farcry3 again. Saw two mercenaries walking down the road, all alone. Quick-killed the one behind, threw his knife into the second just as he turned around. Would have gotten away with it too if two enemy trucks with mounted machine guns hadn't happened to turn a corner. Always, always use the enhanced perception drug...
Farcry3. I kinda want to try an ironman run, shouldn't take long heh.