Happened two months ago:

Went to the cinema with a group of friends, a friend of mine noticed some guys, who he had trouble with before. We got in line to grab some snacks and drinks, as these two dudes come closer and closer and start yelling stuff at us in whatever language that was (guess arabian, turkish, syrian or whatever).

So i start by telling them to fuck off and leave us - We don't want any trouble. One of the dudes get louder and louder and all of a sudden this 5'5 guys starts shooting a double on me and tries to take me down. Well, i'm 6'3 ft and weigh around 270 lbs (and have taken part in exactly 4 BJJ classes, because i can't afford the training fees) so he ends up with his arms wrapped around my waist and still trying to get me off balance. I wrap my right arm under his neck, pull with the other hand and squeeze it in my first ever guillotine. A few split seconds later, the guy gets limb and i let loose.

I have still no idea why and how exactly i pulled that one off, but it worked, seems like my interest in BJJ, even if most of it is in theory and from watching videos really helped in that situation.