You can use Youtube Video Downloader to save your favourite videos. This app is inspired by the famous Youtube app and it works like the latter, the only difference is that with this app you can download them.
To use this app all you need to do is open it, search for the multimedia content you want to see and if you'd like to have the video on your smartphone or tablet tap the 'download' button on the lower left side of your screen. You can access all the videos you've downloaded by tapping the 'folder' button and there you'll see a list of your videos, just choose one and start seeing it.
You can use this app daily to see things on youtube and simply when you find a video that you like click the download button to save it as a video or only the sound. You can download videos in many formats, these are mp4, WebM and 3gp, video or audio only.