Dunno: The biggest profit from non-lethal walkthrough for me was the fun I had
**SPOILERS**
For example, remember the two agents that murdered your parents Page sends after you in an elevator? If you turn on invisibility, they won't get out and you can sneak in, ride down with those guys still inside and walk out and trigger the hilarious line by Page "Barely a scratch!"
Another one - I found a pretty funny way of avoiding killing Navarre. You can kill Alex with a bit of trickery (make him step on a box building a stepladder out of cigarettes and hitting him with a knife and then push the box to a wall) and when you search the body you'll find the key to the exit. Alex will respawn in Hong Kong with no memory of what you did back in UNATCO.
By the way, I was convinced that Paul is invincible in Hell's Kitchen. I didn't help him at all and he slaughtered everyone (not sticking with the prod at all). Has anyone actually seen him die?
Yes, Paul is invincible in Hell's Kitchen.