ImTOO YouTube Video Converter is an all-in-one downloader and converter. It can be used to download videos from YouTube.com and convert them into the following formats: AVI, H.264/MPEG-4 AVC, MPEG-4, MP4, DivX, XviD, 3GP, MOV and WMV. There are even conversion profiles for devices like iPods, iPhones, Blackberry phones, Playstation 3, etc.
This app comes with a web browser built in, which makes it easy for you to find videos and add them to the download queue. At the bottom-right edge of the screen, there is a drop-down menu, from where you can choose the output format of the files that you download and convert. If you don't want to convert the videos, simply select "Same as source (do not convert)". ImTOO YouTube Video Converter can download HD videos from YouTube. All you need to do is select the quality you want from the YouTube page and restart the video.
The trial version of this app only lets you download and convert SD files. In my testing, I didn't experience any problems and the app was really fast, both downloading and converting. The only thing I don't like about this app is that it uses an installation wizard. This might not be a deal-breaker for most users out there, but it is still annoying.