First off, I know I'm providing my solution a lot later than the others, but I've only just got around to the game...
Anyways, something not mentioned by the others is that the Dieselkraftwerk can be used for "stealth kills", as long as you don't hold
as you're shooting - the enemies don't seem to notice that they've been hit by one, so you can sneak in a way behind someone, pop a projectile on their back and then blow it up once you're out of range... their friends come and look, but as you're already nowhere near, you won't be spotted.
I got this in Manhattan in the first section, picking a couple of guys off by hand during it, but the rest were with explosives! The first section was cleared without an alarm & getting 2 Quick Commander Kills in the process.
Don't ask me how I didn't get start the level with the Laserkraftwek, but I somehow brought in the Diesel one from the previous level.