Before the wife and I had kids, I always kept a loaded shotgun under the bed. I showed the wife how to use it and make it safe, then just left it there for emergency purposes.
After the kids came I had to re-evaluate that. The shotgun was placed in a locker, and I had to replace it with a sheathed tomahawk or longknife.
My daughters are 5 and 11 now and have learned that Dad has sharp things around and to stay out of them. As soon as they were old enough to understand, I made it a point to show them how dangerous the tools can be. Fortunetly for me, my daughters have no interest in pointy objects. That may change if a boy is in my future, but thats a bridge I'll cross when I get there.
As the girls arent infants anymore I leave an unsheathed kukri beside the night stand for suprize night time visitors. My knife collection resides in a unlocked drawer, and most firearms are under lock and key (with one exception, which is kept where little hands cant get to). The girls know that Dad's knife drawer is off limits unless Dad is with them and is helping them get what they need.
I think the best thing I have done was taking my daughter to a hunters education class when she turned 11.
She was taught hunting ethics and safety, as well as firearm safety, which was discussed heavily.
I was suprized how much of the safety lessons carried over to even how she handles knives! I was very happy with the outcome of the class.
Also, attend the class with your child even if you have already taken it. I had a really good time discussing the class lessons with her after the class was over.