Only irresponsible things I ever did, I did alone, so they don't really count, right?
There was a stretch of old back country highway that had a lot of dangerous curves I used to enjoy speeding through in the wee hours, with no headlights on.
~Disclaimer~ That road was pretty much deserted and in all the times I did that, I only ever encountered 1 other vehicle. Which was also speeding with no lights on. Fortunately, that was on one of the few straightways. I'm pretty sure the person driving that car was drunk though, cuz I watched him swerve all over road straightway in the rearview. That was back in the days before cellphones were commonplace or else I'd have called the police and reported him.