In fourth class, 1989, we got a substitute teacher in from Caherciveen (it's funny the things you remember) who would grind his knuckle into your shoulder, saying "Don't vex me now". I still remember the look on his face when he read my mother's letter.
In first year, 1991, there was an old Brother who still ran the computing lab (for some reason). We were in our first class of the year, all excited about learning computers. There were all kinds - old Apple II's, an Apple III, a Siemens-Nixdorf 8086 with 12" monochrome screen, an Amstrad 286, and various others. And one Mac Classic. I don't know what we were doing on the Mac, but it suddenly froze and I, with all the authority of someone who had a C64, promptly hit the reset button to clear it. The Brother saw me, came over from behind and gave me a clip around the ear, shouting at me to never do that again.
There was a geography teacher in the same building who had everyone who didn't do their homework stand up next to their desks. He'd then come down to you, stamp his much bigger foot on yours, then rub the sides of your head with his hands. But it was harmless, everyone, including those who got the "punishment", were laughing. I really liked him, he was a funny guy. Shame he retired the next year.
There was a Spanish teacher who hated Spanish people, and was known for being banned from many bars across Spain. He'd devise all sorts of punishments if you crossed him. It was Transition Year, 1995, and I had been studying French all this time. I was in Spanish as part of TY's "experience everything" schtick it had at the time. I didn't know what the hell he was asking me but apparently I was supposed to know it, so he opened the window (we were on third floor of the school building, itself on top of the hill in town and well exposed to the wind) and shouted at me while the wind and rain tore at my books and notes until I got whatever it was.
He was hilarious, too. I'd hate to be any more of a pupil of his than I already was, but he'd be a hell of a man to listen to in a pub :) Ah... none of that nowadays.