OK this is going to sound weird but ever since i been trainning in kickboxing, i notice whenever i walk by someone, and they are walking by me, i notice opennings for a strike like a jab or a left hook lol. I notice the distance, and what their own attack and defense maybe in my peripheral vision. I can see the body langauge of a fighter or if they're an athlete, I can sense if someone's about to approach you into your comfort zone (squaring off) i can feel the danger and my body naturally gets out of the way or goes into rhymnn ready for self defense. People testing each other's defensive body langauge. Like when i walk by someone who's carrying his backpback on his right shoulder, and his other hand is out. I notice in my peripheral it looks like a fighting gaurd. I always get these people, because they can tell you can fight, they want to walk by you (i guess to show everyone else around that they arnt scared) coming to test you. People just treat fighters like we are like weirdo's, i dont if if its fear or what. I notice that sounds of the enviroment are like rhymntic with attack and defense. I know this probally the weirdest threat, sorry if this may be in the wrong section.
I also notice when im about to spar, or watching fights on tv, like..before you begin a fight you look at your opponent and you feel him out with your hands. You know what attack and defense to use before it starts.
I know a little bit of what you mean, but the main things I notice are that if anyone knows you train in martial arts they'll always be the guys who feel they have something to prove, who'll try and give you the I can knock you out routine, and occassionly the ones that actually try to do it( I love these people,lol), another thing that I sometimes find myself doing especially after training a lot of bjj is opening or holding objects with my thumb on the outside, as opposed to the full grip, strange I know,lol.