Grammarly - Clear, effective, mistake-free writing everywhere you type.
Fcitx5 for Android - Android keyboard focused on Asian languages
iTunes - Media player, media library, Internet radio broadcaster, and iPhone device management application
Hacker's Keyboard - Are you missing the key layout you're used to from your computer when using an Android device?
Typewise - The next generation keyboard
AnySoftKeyboard - Android (f/w 1.5+) on-screen keyboard for multiple languages.