Instagiffer is a modern desktop app that creates GIFs directly from Youtube, cellphone movies, avi/mkv downloads and more. It is 100% free, and doesn't brand your GIF with an ugly watermark, or impose size constraints like many web-based alternatives. And best of all, it's easy to use. Just add a video or URL, tweak your settings and voila! You can now post your animated masterpiece on Tumblr, Reddit, Twitter, or wherever.