Back in my novice days of Flash Development, like an idiot I agreed to do a site for some guy at a fixed price. Well, after months and months of making changes and fixes, I realized I was screwing myself -- and, I was beginning to question his intentions. So, as we got to the final days of developing the site, and he asked me to push the completed working site to his FTP for him to view.
At this point, I was fearing that he'd take the goods and run, so I put a small script in there that would look for a text file on my site, and once parsed in, if the text read "yes" then the site would play fine, but if the text read "no" then the site wouldn't play at all. Of course, after I pushed the site to his FTP, I never heard from him, nor did I receive my paycheck. When I called him on his cell (which was the only number he had given me), it was no longer in service.
I changed the text to "no" on my site, and within a matter of hours, I got a call from him. I told him I'd fix the problem, but I wanted triple the asking price. After a modest amount of grumbling he gave in. Thanks for my new G5, buddy!