I hate it when I've known a person for years but when I go to introduce them, can't remember the name 
That happened to me years ago, CLKD. A friend and I had gone along to an event and I went to introduce her to someone there but completely forgot her name. It was really embarrassing - and I didn't have the meno to hide behind!
My mother was a school music teacher and one day, she had been teaching a class of six-year-olds. She was taking a roll-call or something, and tried to remember as many names-and-faces as she possibly could. Then she came to a little boy whose name absolutely escaped her. So she said, "Um....hello. And how do you spell your name?" The little boy (with both front teeth missing) replied, "Thay, Oh, Aith, Enn". Mum felt a bit stupid...........!