GIFs are a great way to make up for the lack of coding wizardry available in HTML emails. GIFs add a little character and fun to your emails and are a way to grab attention. Just be careful not to use GIFs any longer than a couple of seconds, as the image will take FOREVER to load, and make your email sluggish.
Mailchimp actually has a native integration with Giphy, so you can add GIFs on the fly as you design your email campaigns.