Armed MPs pulled M16s on me when I was at the Pensacola Naval Air Station in 1991 and drove too close to the USS Lexington (the training carrier) to get a close up view. Oddly enough, there were no barriers or "DO NOT ENTER" signs anywhere leading up to the carrier. Ah well.
The Marines had 16s on me a few years ago - 1995, I think - when I got lost in southern California and ended up trying to go into Camp Pendleton. Oops.
I used to be an IBM rep, during the college days, and visited both the Lexington in P-Cola as well as MacDill AFB.
I remember the gaurds advice. "When the guys with the M16's tell you to do something, you had better do it as fast as you can."
The Lex is now in Corpus Christie, TX. We spent the night on board last year with my son's cub scouts. It was very cool! I got a bottom bunk so I could lie down on the floor and then roll into it.
15 years ago, I was working at Vandenberg AFB in California and working in a secure area. I screwed up on entering the access code into the keypad to enter the secure area three times in a row. I heard a voice over the speaker ordering me away from the door - and within 30 seconds I had 2 Airmen with their nasty looking rifles pointing at me and ordering me to spreadeagle on the ground.
From that point forward, if I screwed up the access code just once, I'd call for help in gaining access. Rather unnerving.