I have taken some very basic aikido, and have had it come in marginally useful in one instance and very useful in another. in the first, a rather drunk neighbor made some extremely inappropriate comments on my porch that let to an altercation. Being it is usually my first choice to not go toe-to-toe, I spent a fair bit of time redirecting/tossing him, but because he was a fair bit more drunk than rational, he kept getting up and coming back. at the end I was really really ready to just pull out my knife and put him down a bit more directly. H ended up tiring enough to stop trying. In the second incident, another neighbor had a 4th of july party and invited some new friend that started saying some real fucked up shit that ended up getting him his ass kicked. As he was trying to escape, one of my neighbor's friends was working up to shoot the guy, but since his line of sight would have had him shooting almost directly at my front yard, with everyone gathered watching the commotion, I felt it was necessary to not have him try anything stupid. he still had the gun in his waistband, so while looking him in the eye, removed the gun from, dropped the clip, racked the round in the chamber out and handed the two to his girlfriend. the speed it happened at kinda stunned him, and earned me the neighborhood nickname of "Kill Cosby" cause I look so unassumingly nerdy suburban.