I don't practice any FMA's but I do a fair amount of knife training. It's just another possible tool in my arsenal as a soldier. That said, I see no reason (and lots of reason not to) do any partner drills with live blades, no matter your profession or whatever. Like Cord said, if you do that you'll be holding back tremendously to the point of it becoming useless and ritualised. It's innefective for about the same reason bare knuckle step sparring is ineffective. Doesn't do any good if you kill yourself in training anyway. I do a lot of solo practice with live blades (3 and 4 inch folders) but never under any circumstances with a partner. For that I use rubber or wood training knives. You'll know if you get hit and that's all the feed back you need, to know whether your approach is working or not.

It's like force on force training with real bullets. Not a great idea.

Never trained with a sword, my art did not do that. But I appreciate the sword and own one and keep it on my mantel more for visual purposes. But time to time like to pull it from the scabbard to marvel at it. I would have loved to have learned its use.

At the end of my training in self defense we were getting into knife defense however these were not real knives but rather ones made by one of my fellow students out of metal to get the feel and weight however blunt and fat so as not to have to worry about cutting yourself.

Training, definitely would not use anything sharp or lethal. As it takes years to develop any real skill, it is best just to leave that alone. Training is suppose to be as safe as possible with the exception of some bumps and bruises. Introduce something sharp then you not only have to worry about yourself but others; that in my opinion is a no-no.