Friday night at Shodokan we practiced knife disarming. Instead of the more common stuff that we've done in the past such as kotagaeshi, and shihonage, Mulligan had us doing all kinds of eclectic techniques. The one that stuck out in my mind the most is probably one of the most risky.
Slap wrist and the back of the hand simultaneously. This has to be done very quickly and with a good amount of force. After doing this for a bit, my nerves were so agitated that my hand was shaking if I tried to hold the knife in a firm grip. Very fun.