Are you missing an open-source-app? I'm looking for projects!

Hi guys,

I am a professional Java developer and a great fan of free and open-source-software. I recently started to get into Android-development and am currently looking to make the next step.

I got some ideas, but i want to ask the community, especially the guys who are mainly using F-Droid open-source apps. Is there an app (on F-Droid/Open-source) that you are really missing? Looking forward for suggestions :)