I recall when I was about 5 or so, I got a hold of my mom's double edged razor pack. As I remember, I opened up every finger on my hands, and it didn't really hurt, but it felt cold. I also remember my mom walking in on me and screaming to high heaven at all the blood coming out of my little digits.

Does that count as my first knife? If not, then it was four years later when Grandad gave me one of his old used buck pocket knives, and I ended up with it stuck in the top of my foot winning a bout of mumbledee-peg with the neighbor kid.