Utility Knife Stainless Steel - H457-35BSKU: 101-INC 457317 - ARMY-01
One of the best choices. It is small enough to fit in your pocket, strong but not too heavy, and has multiple functions, besides the obvious one.
Whenever you make the decision to engage another person in edged weapon combat, with the exception of Military combat; there are and will be legal ramifications. Remember it is always suggested to escape over anything else, but survival is paramount.