Having to stop ds2 trying to open an upstairs window, because ds1 had told his little brother to go out of the window and retrieve the tatty railway magazines we had put in the bin the day before.
Ds2 was kneeling up by the window, pushing it as hard as he could - he’d opened the catches, but thankfully the window stuck, otherwise he would have fallen out head first. 
Letting ds1 eat Doritos out of the bin. I have told this story on MN a number of times before (mainly to reassure another mum that they aren’t the worst mum in the world, because clearly I am) - ds1 was in the worst of the terrible twos, and had had a monumental screaming session the night before and, at 8.30am the next day, had already been screaming for 45 minutes, and I was at the end of my tether. I was on the phone to dh, sobbing that I couldn’t cope - and the screaming stopped!
I hung up, and went to investigate, only to find ds1 standing by the kitchen bin, eating the tortilla chips we’d had left over the previous night, and had thrown away. But that isn’t the worst bit - I looked at ds1 and I knew that taking his delicious bin-snack away from him would start the tantrumming again, and I just couldn’t face it, so I let him carry on!
Eventually he got bored and wandered off, and I found somewhere more secure to keep the bin - and he must have had a bomb proof digestion, because he had no ill effects whatsoever.