My current favourite:
"Arsenic Rain"
The first ideas were:
"Arsenic Bowstring"
"Sagittarsenicus"
But, slightly more in tune with jmdt's usual naming style, maybe one of these fits:
"Catch! It's Arsenic!"
"Someone see my Arsenics? Must be flying 'round somewhere"
"Fly and be free, my little poisoned daggers!"