I think i've patched up more roofers than anything else on the job, grizzly lot that they are One foreman admonished his wounded crewman bellerin' "You weren't hired leaking were ya"
As a low voltage tech I spend a lot of time in drop ceilings, my worst enemy are the cut ends of the 1/4" al bars they use to hang mounting brackets on, the nice sharp cut end has a knack for ending up in my scalp. When around the house every now and then, usually when I am trying to finish up fast, the box cutter vs thumb while cutting NM wins.
I'd suggest using a hard hat or a pitcher's helmet if you're working inside a plenum....scalp cuts are nasty....especially when you get hair in them. And who knows what kind of nasty stuff is living on that crap in those ceilings.
Ditto to cut NM cable....what about using a cable ripper and side cutters instead of a box cutter?