Suggestion: don't buy a knife for "coolness". (No one has ever defined coolness to my satisfaction.)
The idea of using a knife for civilion self-defense is pretty much a fantasy, unless you have a good deal of training and practice. Rather than just being robbed, flashing a blade could get you killed.
A handgun is one thing, a knife is something entirely differant.

"there is nothing so frightening as ignorance in action."