Wait until you unlock Zero's ability to shoot through enemies. I had a combat engineer lined up for a headshot earlier only for one of those robo walker thingies get in the way as i fired (i had already weakened it a bit). The shot blazed through the robot and killing it, but it still nailed the engineer in the head, scoring an instant kill. Was grinning like an idiot after that!
Girl, you thought he was a man, but he was a muffin.