Things that make you say D'OH...

[Dwayne]

...Or dumb things we do.
Flying my 1/2a Pathfinder today and couldn't understand why it was so slow even though the Big Mig 061 was a screaming, I dorked it a bit (no damage) but when I wiped the prop off I noticed it was on backwards. D'OH! 

[Dan Berry]

A good friend of mine flew his Nelson 36 FF plane with a prop on backwards.
He wouldn't tell me until the day was over.
It can happen.