I have a folder labeled fun. This way students are aware that these apps are for specific times of the day. Doodle Buddy, Draw Free, and Virtuoso are fun. This may be on the list, but the app Talking Tom 2 is great. It repeats whatever you say in a cat like voice. It is really funny and would be a wonderful tool to use for students who need to verbalize wants and needs.
When searching for an app from the app store, you can click on price and have the store only show apps that are free. That saves a lot of time. Good luck!