You can turn a video into an animated GIF using the latest version of Apple's free Keynote presentation software. A new feature of Keynote is the ability to export as a GIF. To convert a video, you can create single slide presentations using the video and export. You can also easily crop and trim the video, as well as add text or combine multiple videos to a GIF.
Check out Make an animated GIF video from a Mac on YouTube for closed captions and more options.