I’ve just found this site and am rather excited. I apologize in advance if I do so go on. 
First my worst as far as how badly it could have ended:
I was on the highway a few minutes driving home and glanced in the rearview to see I had forgotten to strap in my toddler in his car seat! He was just sitting there free as a bird with no restraint at all. As usual I had many things in my hands when I got to the car and just sat him in his seat while I unloaded. Then forgot I hadn’t strapped him in and closed the door. Yikes!
Next my worst for the affect it had on someone elses day:
My husband drove back from the cottage in his vehicle before the kids and I in mine one weekend. He took the laundry bag I gave him. After he left I realized that my keys (car, house, everything) were in a pocket of a pair of pants I was wearing earlier that weekend. Those pants were in the laundry bag my husband took home. It’s a 3 hour drive and he has no cell phone. I had to call him after he got home and get him to drive back with my keys so I could go to work on Monday. He had to make that 3 hour drive 3 times that Sunday. I always put my keys in my purse as soon as I get to the cottage now.
One of my personal best: I had a thought that it would be nice to call so-and-so (old family friend like a 3rd grandma). It had been awhile. Then I realized she had died months before. That was a shocker. OK maybe not ADD, maybe just repressed, but truly scary to realize.
There are many many more.
– Dogs left outside all night..
– Forgot to get gas before I got on the highway to go home after the empty light came on on the way to work (thank god for CAA).
– Birthdays I remember a month before sneak up on me and run past before I know what’s going on (almost always).
– Forgotten anniversaries (about half and half).
– Forgot to leave $ under my sons’ pillows from the tooth fairy. Yes I said sons’ as in I’ve forgotten it for both of them. I told them I forgot to call the toothfairy and tell her there was a pickup at our house. One time I forgot 2 days in a row for one son.
– I NEVER remember peoples’ names when I first meet them. I swear it’s like their name gets bleeped out when they say it because I just don’t absorb it. Crazy head of mine just disregards unimportant things like people’s names (hang my head in shame).
– Get to a room or to the top of the stairs and realize I have no idea why I’m there. Give up and go back and then see something that triggers the memory of why I was going there in the first place. Go back up. Lather, rinse repeat.
– Go back into the house to get something only to find a few other things I forgot to do/bring and then lock up again and start walking to the vehicle only to realize that I still didn’t get what I went back in for in the first place and we’re late (again) for school/work.
I’m sure I could go on but I guess I already did.