Flash Video Downloader allows you to download flash videos from most websites. There is one condition that has to be met for Flash Video Downloader to be able to download a video from a website and that is that the video has to be set to autoplay. Most video sharing websites do this by default. I did my testing of this app with YouTube and I found that the app didn't always work the same way.
The first video that I added wasn't downloaded. But then I added another video to the queue, resetting the first one, so the application would attempt to download both again. And the first one worked this time, but the second didn't. They were both YouTube videos, so I don't know what might have gone wrong in each case.
There are a couple of interesting features to be noted. First, Flash Video Downloader has a login window that allows you to type in your username and password. This allows the app to download videos from sites that you have to login into. Also, the app has notification support, so every single time a task is done successfully or a download fails, it will let you know. There are a few other customization options in the 'Preferences' window.