Can't really name one that I'd call stupid, really. But I can name a crapload of stuff I didn't get in trouble for, like that time I drove a chair around the classroom like a car making vroom vroom sounds. Or the countless times I played my Gameboy in my desk during class. I got a couple funny stories about that.
One time I was playing through Pokemon for a friend who started a new game after trading me his old Pokemon. I spent a class trying to beat Brock with his old Mewtwo, who would not listen to me. Have you ever seen Brock's Onix beat a level 100 Mewtwo? I have. That took an entire class, since I was apparently too stubborn to switch out until one of use fainted. I got called on it once, and was forced to leave it on and waste the batteries while I actually did some work, but that was it.
And then there was the time I was playing Robopon, and upgrading my business. If you haven't played it, the Robopon cartridge is larger than normal to keep track of things in real-time, and when your upgrade is finished in game, it makes a loud ringing noise, even when the game is off. So imagine me in a quiet class, everyone's studying, and then a very sudden, very loud ringing is coming from my desk. And I kept doing it. Several times that day the class was interrupted by a loud ding-dong coming from my desk. All I got was a few weird looks.
And I don't remember this one first-hand, but my mom heard it from my principle once when they spoke. At one point the principle caught me playing in my desk and pulled me from the classroom to quiz me on the class. Apparently I answered perfectly, and was sent back to class.
I'd like to say that's why they were so lenient, but I remember half-assing most of my stuff in school, so I can't say in good confidence that I got straight A's or anything. I started homeschooling during the fourth grade too, so I don't have any recently memories of school either.