We use live tanto for yudansha exams, but I've already covered the reasons why previously, suffice to say we are not trying to recreate a realistic environment but have other reasons.
Anyway, funny thing happened last night at training. Using a wooden knife I was teaching our beginners tantodori to some white belts. One of whom had done ninjitsu before and was treating it a bit like a shuriken (i.e. thought that throwing it at the other person was what we were trying to do). I explained that we wanted to make sure we didn't disarm ourselves and that if I had the knife concealed he wouldn't know what was coming anyway. I demonstrated this by stepping in and starting a shomenuchi by cutting up towards his neck (the intention being to make him move his head backwards and so expose his throat). He responded by reflex I suppose and stepped in and punched me in the stomach, so I stopped the attack before it made contact with his head (it was obvious that he wasn't paying attention to what I was doing and I didn't want to hurt him). I stopped the tanto and then he actually jerked his head forwards
into the blade.
I stopped the attack before it made contact and he headbutted the knife.....
Mike