I know you didn't ask, but I'd seriously evaluate your "knife for self defense" idea. If you can't defend yourself without a knife, chances are you can't defend yourself with one.
That said, if you want a knife capable of killing or disabling someone, (really what you're talking about when you say 'defend yourself') you can't do much better than a Spyderco Harpy, or a Civilian if it's legal to carry.
