What is the most reputable Tactical Fitness Trainer certification? I understand that NSCA’s TSAC-F is reputable.

Yes, TSAC-F is in my opinion the best one out there. I have been to a few of their conventions and conferences and I liked what they presented. Also having NSCA as the organization behind it, is very important because of the support and resources available at all times. I would strongly advise him to give them a try.