I can get a few good examples just with a milk jug alone. On occasion I simply try to put it in the wrong place in the kitchen, such as in the small, black refrigerator (the milk is stored in the big, white one that's nearby), or up in the cabinet where the cups and bowls are. There was even this one time where I took it with me all the way to the other side of the house, where the pantry is, instead of the cereal.
But what I did the other day makes me wonder if my brain is degenerating. (Well, at an abnormal rate, anyway. ;p ) I took out the milk and put it on the counter. Then I got a cup out of the cabinet. Then I went back into the fridge as if it were the first time, not being able to figure out where the milk had gone, and swearing that I had just seen it. But then I saw the orange juice and decided to go with that. So I poured myself a glass of orange juice, with the jug of milk going unnoticed nearby, just within arm's reach. I then put the orange juice back. And when I turn around to return to my cup of orange juice... I notice the milk. And so I spent a few minutes just standing there, trying to figure out how it could have been possible to do what I had done. I still don't believe it.