Not to ruin the thread, but many of my mindf*** moments have been in the realm of music.
When I first heard the rapper Drake, I though that he was a bada** thug that rapped about his life and was hard. Then, I come see how he looks like and his mannerisms outside of the booth and I'm completely shocked. He isn't a thug, and he's actually a nice guy. His stage personal and his actual self was a real mindf*** for me.
Another example is Nikki Minaj. I first heard her rapping in the song Bedrock, and when I heard her, I was confused, thinking, "Why is a 12 year-old girl rapping about her vagina and wanting to have sex?" I come to find out that she's actual in her 20s and is 80% fake (i.e. she wears a lot of make up, costumes, fake hair, and has had a lot of implants). There's an 8 year-old English girl that sounds exactly like her and is even more talented. That was a real mindf***.
Lastly, when I heard the chorus for the Gotye song Someone That I Used To Know, I thought that it sounded good, only that I didn't know the title of the song. When browsing for music, the song was very popular and was prompted to find out why. The first minute and a half didn't really impress me and I was going to move on until I hear the chorus roll up. I couldn't believe that they were one in the same. Total mindf***.