Jay Pique writes:
So the jack-knife is no longer sufficient for opening Christmas
gifts. [...]
After a couple of near-misses I grabbed the snips
from the shop and had no trouble at all. Scissors don't cut it; you
need the mechanical advantage of compound action - the plastic is that
tough.

I have a set of heavy shears sold by Olfa that I use to open blister
packs that have been welded shut. They're sharp enough and heavy enough
to cut the plastic effectively (and they'll also cut thin metal like
shim stock). I suppose the compound aviation snips would work too, but
I've never needed the mechanical advantage, and they're slower.

Dave