Documents (from the company Readdle). It's similar to Goodreader, but it's free and in my opinion it has better performance. It's rather flexible in moving files between iPad and computer. The app allows you to turn the iPad into a "wi-fi drive," in which it appears to the Mac as a hard drive. You can simply drag and drop files from the Finder, and it all transfers quickly over your local network. If you'd prefer a cloud-based solution, Documents also has support for Dropbox and Google Drive.
While I use Documents primarily for PDFs, it can handle many other file types as well, such as video. It is easily among the top five apps that I use on my iPad each day.