Well, I'm still living at home, and I've started collecting knives, including a couple khukuris and a (functional) katana. They are fine with it, but my grandma is convinced that someone is going to break in and cut my entire family to ribbons! Her husband is an avid hunter too, go figure.
Now guns on the other hand...I think my parents would flip if I bought a gun. I may have to wait until I'm out of the house to get myself the guns I'd like.