GIFs are commonly used on the internet and are great for reactions. Have you heard of a cinemagraph though? These are a little artsier but nonetheless cool.
Cinemagraphs are similar to GIFs but are more akin to a photo. You could even say they are a marriage of the two.
Cinemagraphs.com shows great examples of the medium. If you take notice only one thing moves in a cinemagraph.
If you have photoshop and a phone you can make a cinemagraph of your own.
Take a 10-20 second video of anything. Just make sure something small or simple is moving in the photo. I would suggest pouring water into a glass.
Once you have got your video, upload it to photoshop. Next, you would want to cut down your video. If you are using the example of the glass and water, trim the video from where you start pouring to just before you are done pouring.
The last two steps are to take a snapshot of the video and put it into a video layer above the moving video. Make sure both layers are equal lengths. Lastly, make a layer mask and draw over the moving water.
Once you play this back you will see that the water is moving, and the rest looks like a still photo. To save make sure you choose the option to save as a web legacy. Now you can drop this into a browser and watch your masterpiece.