I was ordering some shipping supplies and found what may be the perfect 'kite knife'. It's only about $8USD...cannot cut up the kite like open knives...but will pop those strings loose in a heartbeat.
This one is meant to be used to cut the plastic stretch film they 'mummy' numerous boxes together with.
Any of you in the US can read the phone and part numbers. If you are outside the US, I'd be more than happy to send you one. I suspect the post would be about $3.
.....let's hope I didn't bugger the image this time!