Yesterday I reviewed "Deus Ex: Human Revolution." You can read that review if you want, but, long story short, the game's really damn good and you should pick it up. One of the unique features of "DXHR" is that you can play through the entire game without killing anyone (save for the bosses, who totally deserve to die anyway). If you actually manage to make it to the end of the game without killing anyone, you'll be rewarded with the Pacifist achievement/trophy, a true accomplishment.
Because I'm a crazy person, I decided to go for this achievement on my first time through the whole game. And I succeeded! Now I'm here to share with you some pointers on how you too can succeed in the ways of non-lethality. This guide won't have any spoilers, but it will have tips on which augmentations to pick up and which weapons you should have in your inventory.
Note: You'll still get all the story elements from playing through the game non-lethally, but if stealth isn't your usual style, I'd suggest playing through the game once however you want. Stealthy players should feel right at home playing non-lethally, though.
TIP #1 - Select The Hardest Difficulty
If you're planning on going non-lethal, you may as well select the hardest difficulty. Not only will this net you an achievement at the end of the game, it won't make the game much harder, as the difficulty only affects the amount of damage you take and enemies can still be knocked unconscious with one hit. If you follow this guide, the only time you'll take damage is when you fight the bosses, and those sequences are pretty manageable compared to the rest of the game. By playing this way, you should also be able to finish the game without setting off any alarms, which will earn you yet another achievement.
TIP #2 - Don't Kill Anyone In The Prologue
I'm not 100% sure if kills during the prologue count against you, but you're better off not risking it. You won't have any augmentations at the beginning, so it'll be a matter of mastering your ability to move from cover to cover without being spotted. This skill will be mandatory later on in the game.
TIP #3 - Keep Multiple Saves, Hide Bodies
Don't rely on the game to auto-save for you. I'd suggest keeping multiple saves going so you can reload to a safe spot if things get too hairy. If you accidentally kill someone, reloading a save to a point beforehand will allow you to keep going for the achievement. Also, hide bodies carefully, as an unconscious body spotted by a guard or camera will sound the alarm and make your life a lot harder.