A lot of BDSM advice, especially for rope and shibari recommends the use of EMS safety shears for emergency cutting of ropes. These are designed for cutting quickly while keeping a flat, non-sharp part against the skin. They are way better than regular scissors so don’t confuse them with normal scissors (which are not very good at cutting rope…especially in a hurry.)
You can get them here for $12 http://www.amazon.com/dp/B002L9QML4
The benchmade is my choice as the best for BDSM emergency cutting tool. It’s small, easy to use and cuts rope extremely effectively. It also comes with a handy little case that can be attached to the strap of a rope bag -which is really perfect as there is no digging around the bottom of your bag for it — and it is also clearly not a weapon so you can get it past the bouncer at BDSM events in clubs.
This handy little tool will cut ropes far faster than EMS shears: especially if you are using thicker rope.
One thing about this though…don’t use it for anything but emergency cutting — you want it as sharp as possible when seconds count.