Pretty much anything the guy who sits next to me in my computer graphics class says.
He asked me how to do something extremely simple (how to make one of the pre=set shapes in 3DsMax, I think it was a pyramid), and I respond with "It's the same way we've always done it."
"I don't know how to do that."
The guy who sits to my right cuts in with " You know, (name withheld to protect the oblivious), after nearly six months of working with these programs, you should really know how to do this."
After that little exchange, I found the largest Picard Facepalm I could, and left it on one of my monitors for the rest of the class.
Edit: Well, it wasn't a "Did I really just do that" moment, but you get the idea. More of a "Did he really just say that?"