I apologize if this link has been posted before. I believe it's relevant to the topic of this thread, as this is what you're likely to face if the knifer is even moderately skilled with cut placement.
http://video.google.com/videoplay?do...k+vs+gun&hl=en
Basically, I advise a whole lot of fast backpedaling during the draw and shielding yourself with your non-shooting hand. Then RUN away while shooting.
If you just stand there and draw, you're going to be dead or dying when the ambulence arrives.