Back when I ran Twilight:2000, I read (somewhere) about the M2HB having (at least originally) an optional clockwork mechanism which could be attached to it's tripod that - once tripped - would allow it to automatically traverse the gun through a set arc while firing controlled bursts. So the next time I set an ambush and the PCs rushed the ambushers according to approved doctrine, I had the NPCs run away but activate one of these as they left. They got away clean while the PCs carefully stalked the (long-abandoned) machine gun nest.

As the the hearing and eyebrows thing . . . 

I just finished binge-watching the BBC "Torchwood" and there's a scene in the final season where someone wants to delay someone's response time without actually harming them (much). So he fires off his 9mm handgun right beside the fellow's unprotected ear . . .

In another scene earlier in the same season, someone in a hovering helicopter fires an RPG into a stone house. Miraculously, the rocket sales in through a window, through the open room door, down an interior hallway, through a second open room door, through a second window, to finally explode against the stony hillside behind the house. In response, a mother holding her baby on her hip snatches up a set of earmuffs (it's winter), deftly flips these over the little girl's head then advances down the hall to the first window, emptying her handgun out the window at the still-stationary 'copter as she walks. We see sparks fly from the 'copter's frame, then the RPG guy slumps over. The 'copter soars away and the mother looks down at her baby (paraphrased from memory): "Let's hope that settled them."

Scenes like this make me wish Torchwood had gotten more seasons.