Top 3 for the letter G

1. Guitar Hero Live (Free w/ in-app purchases)

You have to buy the guitar in the store, but once you get that you are rocking out.  Play the bluetooth controller guitar with popular songs from all across the decades.   

2. GPB Now (Free)

Georgia Public Broadcasting has a great amount of original content.  You also get the popular PBS stuff as well, at least what they are licensed to play.

3. getGIF (Free)

Browse thousands of GIF's online.  Save your favorite ones and come back and watch em again.