I have a couple that come to mind right away. I'm such a dork embarrassing myself is a daily occurence.
When I was in college our apartment was freezing cold, so you had to sleep in sweats over your jammies so you didn't freeze to death during the night. It was like something from The Exorcist, you could see your breath when you got up in the morning. Anyway, one morning I woke up late for class, got dressed and then grabbed my hoodie and tied it around my waist in case I got cold. I got to class on time, everything went fine until I was walking out. A guy taps me on the back, and hands me my pyjamas that have fallen out of my sweatshirt :|
On another occasion I was working temporarily in an office, and the permanent employees were trying on new uniforms to see what they liked. They were trying various different styles of navy blue trousers, and asking me what I thought of them. One lady came out, and I told her that those ones didn't fit so well and looked a bit too tight. It turned out they were her own and she was done trying on clothes.