Gboard - Google-powered keyboard with search, GIFs, emojis and more!
Emoji Keyboard - Allows searching and inserting into other applications near thousand emojis.
Grammarly Keyboard - If you want your mobile writing to truly shine with its polish, you need the Grammarly Keyboard
Swiftkey - SwiftKey keyboard allows for seamless typing and adapts to the way you type, so you can spend less time correcting typos and more time saying what you mean.
Hacker's Keyboard - Are you missing the key layout you're used to from your computer when using an Android device?
AnySoftKeyboard - Android (f/w 1.5+) on-screen keyboard for multiple languages.