Generally, there are no "accepted everywhere" certs. The closest you're going to come to that is POST certification classes which are usually limited to LE. I've taken a lot of those classes both as a student and taught more than a few as an instructor. Unless you're LE, the certs count for nothing (unless you're training others), even then, they only count for the organization you're training for. Most of the stuff I have done has been with NTC, I previously did training with some former LAPD swat guys who did a lot of LE training. That was much less structured and controlled than NTC is. I will definitely give NTC the thumbs up as far as being top-notch training, granted, it's very LE centric. As far as military style stuff, I think Max with TFTT is still around, they're very military oriented, and did a lot of training classes for units deploying to the ME from about 2003 onward. However, these may be a bit advanced, and I am not sure they take singles.