Image Transform to convert animated GIF to static?
Is this a one-off image or do you need to use the transform for a bunch of GIFs?

There's no way automated way to tap into transforms currently. (Craft 3 is going to be much better in this respect.) 

The other hard part is you're probably going to want to specify what frame of the GIF to use. (Fun fact: years before browsers supported animated gifs, they would simply show either the first frame or the last frame.)

If it were me, I'd set the static frame manually using whatever method you want (Photoshop, Imagemagick/gd on the command line, etc.) 

Then use a custom field on the asset to relate that static gif back to its animated counterpart.  Unlike in other CMS, this is where Craft really becomes powerful.