I saw this on With Leather but I had to re-post it here...
Fast forward to 1:25 to see the slow motion reaction shots. My favorite part comes a few seconds later at 1:43 when, despite the target falling to the ground in pain, the tennis ball machine continues to fire. Coming in a close second was the computer animation of the nut shot at 1:53.
If you perform a google image search for 'douche bag,' this is the guy that shows up first:
Now you know.
EDIT: Apparently douche baggery is a very dynamic field. The picture above is no longer on the first page of images returned when searching google for douche bag. Who knew?