Well I guess what you do with it is up to you, but I've found jDownloader to be useful for many things. It captures any link you copy to the clipboard and has plugins for hundreds of types of sites and the plugins for the popular ones are frequently updated. It doesn't bypass registration, so if a site still needs an account you'll still have to provide details, but they do try to stay on the right side of the law like that.
I've found it kinda handy when grabbing reference videos of arcade game recordings.
Only real downside is it being Java.