I'm really liking Coubs right now. Here's a fun one.
As you can see Coubs are looping videos with audio. There is a key difference between a Coub and a Vine or Instagram video. You can add audio to a Coub that's longer than the video. While the video only loops for up to ten seconds, the audio will play all the way through before it restarts. Vine and Instagram videos have audio only as long as the video itself.
Audio in looping videos can get annoying. But I think that's mostly due to the repetitive sound. With a continuous track, that annoyance is greatly reduced. Between Coub, Vine and Instagram, I will choose Coub...but Gif's (and silent webm) are still my favorite looping video format since they are silent and versatile.