While the number one threat around St. Ned's is, of course, bears (if Stephen Colbert is to be believed, and clearly he is), I think we have Homeless Guys With Knives as a distinct #2.
Someone left the classrooms unlocked last night, and it was pouring down rain so two men found shelter in there. Which, eh, whatever...except that when Dennis came around early this morning to set up the rooms, one of them jumped out at him and put a knife to his chest.
Of course Dennis, being Dennis, diffused the situation and they went away, leaving behind only a giant mess in the bathroom and one seriously shaken-up sexton.