Depends on what you perceive as 1) cool and 2) tactical and your budget.
1. is very subjective and you will know if the knife makes you smile.
2. Good suggestions here on Emerson, Utilitac and Cold Steel, Talwar and others as well.
3. Is up to you as well.
A strong lock, strong tip, good spine and a handle that affords significant purchase (both ways, fore and aft) along with a blade of sufficient length to reach parts that when reached neutralize the assailant's ability to attack - for a while or forever.
Though I favor Emersons for this function any one of my beater large or extra large Cold Steel Voyagers would do just fine as would suggestions in this thread.
Remember this however, that you are no more armed because you carry a gun (or a knife) than you are a musician because you carry a guitar.