Which programming language is best for android development?

Can we add a FAQ sticky or something that has my and other's inevitable answer to this question:

What do you want to make? Please be more specific than "Android Apps". If you want to make games, I suggest learning Unity, regardless of your target platform. If you want to learn to make generic Android apps, learn Java (but just version 6 - last I checked Google hasn't updated it to handle version 7 or 8, and they said they weren't planning on ever making it handle those).