Unarmed vs. Knife

[TheOneRonin]

Here's a little thought exercise for the community.

Given an exceedingly skilled but realistic martial artist (skill(s) at 16 - 18 range plus a few improved techniques), how would you go about disarming (or dealing with) an assailant armed with a knife?

I'm looking for melee combat approaches, not answers like "run", "bargain with him", or "shoot him".

Martial Arts and Technical Grappling offer a plethora of methods for dealing with this sort of situation, and I'd like to know what the community members feel is the most effective/efficient/safest way to deal with an assailant armed with a knife when you are unarmed.

In addition to seeing your options/tactics/techniques of choice, I'd like to know WHY you would choose that method over any of the other options available.

EDIT

For those who see how many pages this thread has grown too and would like a TL;DR, I'll summarize the tactics people have mentioned so far.

In no particular order...

1. Judo Parry to Arm Lock (then anything after that is just gravy)
2. Karate Kick to knife hand (with lots of DA to reduce the parry chance)
3. Judo/Karate attack to Disarm (with improved Disarm technique from Martial Arts)

The jury is still out on the "Retreating parry to feint stepping to non-weapon side to Arm Lock the non-weapon arm" shenanigans, so I'm not going to put it in the list.