This is such an interesting subject and yes it does happen. I love the idea of trying to pick a fight with a complete stranger. I was a student at Leeds University for four years and that was where it was easiest to make it happen. It probably worked on about half the times I tried it
I would try most often at parties. The trick is to pick the right potential opponent. One typical time was a girl called Katie. It was a student party in a student house, and I was just in the mood for a fight. I picked this girl out early on, I didn't know her but had seen her on my course at lectures. She was about the same size as me and there with her bf. That is imporntnat, it gives a possible reason for the fight.
I studied her for a while then waited for a chance to go up to her and her bf. I just said to her 'hi my name's Jess'. She said 'hi I'm Katie and this is Joe.' Then I just said to her 'I want to have a fight with you.'
She said 'what did you say', already her bf was looking on amazed. I told her again and she asked why. I said 'cos I want to, cos I don't like you, cos he's cute, maybe we should fight over him.'
She just sort of laughed and told me to get lost, but I knew what might happen next and took my time. I kept them in view. They were talking a lot, and yes, as expected, it was Je her bf who came over to me after about 10 mins and asked if I was serious. I could tell how excited he was. I told him I was, he told me to wait. Then after more conversation he came over and told me she would, and where and when would we fight. I told him that they should meet me outside at the bottom of the garden in 20 minutes.
So it can happen, that approach probaly worked for me 5 or 6 times at University, in a bar, at a party or once in the library!