not since I was 22. I got into 2 fights over girls when I was a teenager - one was actually my best friends girlfriend, somebody insulted her, I beat him up, and she ended up making out with me. I was 13 or so. when I was 16, somebody grabbed the ass of a girl I was walking with, she slapped him, he swung at her and I ended up in a full fledged fight with him. both of those were stupid, but if I was that age I'd do it again.
when I was about 21 or so, there was some guy who was flirting with my girlfriend really seriously. he was an american student on junior year in israel, and he thought that he was pretty hot shit. my girl wasn't really interested in him, but she liked the attention and I wasn't around during the week. I was in a course at the time that was very important to me, and I didn't want to be distracted, so I wanted to make sure he understood that he had to stop. so I basiclally told him that I would kill him and bury his body in the dessert if he every talked to her again. I actually was serious, and I think that he believed me cause it worked.