Distortion
A couple of weeks ago we took some pics at a Pub in sydney. The BBQ took a turn for the worse and erupted in flames which totally destroyed any hopes I had of getting a free sausage but wile flames were billowing out I snapped a few pics with a 16-35mm lens. When I got home and had a look at the pics, I thought there was something wrong with the lens but its just an extreme case of barrel distortion>
It looks extreme because the make shift fire fighter (now cone head) was at the outside of the frame and on a different plane of focus to where I was pointing the camera.
Weird :P

