Its important to carry something that's legal if you plan on using a knife for self defense. As far as a legal knife you can carry that's designed to cut really deep, nothing beats a hawkbill. You could eviscerate someone with a single swipe with one of these. I tested one out on a deer carcass that got tainted, and these cut very deep, very easily. When you swipe through, you can make a deep cut without a whole lot of resistance,. It doesn't even feel like you cut deep, until you examine it more closely. Flip your wrist into it when you swipe. Mine is sharp enough to shave with. If anyone knows of a knife that's 3" or under that can do more tissue damage easier than a hawkbill, let me know.