What do you use for IM on smartphones?

The social networking market has been divided and relatively stable for a couple of years now, the main move is in the market of instant messages on smartphones and tablets. I wonder what the situation is in the geeky Russian-speaking environment. The previous and somewhat similar survey on Habré: Communication on the Internet: earlier and now .

No need to specify the applications that you actively use, but not just for IM. Such may well be Skype, Twitter, Facebook, VK, etc.