Mystic line cutter from Airborne in Osborne Park around $14. It's double bladed and comes in its own pouch but tends to get lost due to how it is secured in the pouch.

Cheers
Rich

to be honest i dont see the use in one seeing that you can completely detatch from the kite without sacrificing lines.. that and the blades rust out after a season or two and become rather useless

oh righto didnt think of it that way my bad. still their blades do rust so if u end up getting one make sure u rinse in fresh water and let it dry instead of leavin in pouch to dry

Thanks very much, I'll get one tomorrow

Last summer, whilst trying to help some fellow kiters that had got into trouble, I found myself about a Km offshore after sunset with my arm wrapped in the lines of a looping kite (I was also still hooked into mine which was still in the air).
I have a Dakine knife like the one in Reli's photo attached to the strap of both of my harness's and so I was able to cut myself free and kite back to shore.
The knife was probably about two years old but still cut the lines easily, it probably helped that they had heaps of tension on them. Even though the knife worked fine I went out and bought a new one to replace it, $15 (from memory) is a small price to pay for something that may save your life.

I think all mystic harnesses come with a hook knife in a pull-release vecro pocket. Haven't had to use it but always remind myself it's there if I'm going out in waves...