Currently in West there are some notable Messengers that need no introduction: Facebook Messenger, Apple iMessage, Whatsapp, Kik, and BBM.
In Asia the collection of names are entirely different:
When I was in Tokyo, the girls showed me their messenger apps. LINE is huge in Japan, whereas Kakao Talk is more of a Korean thing. One thing that’s in common with the messengers in Asia are the virtual stickers. It’s basically an emoticon or Emoji but much larger (take a look at the GREE screencap). And the girls love that feature. It’s also worth noting that it’s one of the main sources of revenues (you can purchase or gift these stickers to your friends). Tencents WeChat separates itself by integrating itself with the hugely popular Tencent platforms such as QQ. Naver on the other hand is seemingly rolling out an unlimited stream of applications and games (most are free too without ads!) that you can use to enhance the messaging you do with your friends. These include Social Games such as ZooKeeper, and LINE Brush which is a social drawing tool.
In the end though, I think the strategy for the Messenger is simply just a platform to collect a growing user base. Almost all of the apps in Asia have some sort of integration to their already released games, social media sites, or stores.
There is great potential in this space and almost none of these apps have any sort of integration with the computer yet (you can only send messages on your Mobile). The only ones that allow you to send messages on your computer are mainly American (eg. Facebook Messenger, GTalk, and Skype).
I hope I provided you an interesting but brief summary of the current state of Messaging Apps around the globe. Oh yea, and btw ICQ is still HUGE, especially in Eastern Europe. So if you’re planning on traveling abroad in the next few months and meeting new people be prepared to download a bunch of new apps!
PS. I think the reason why Tencent created WeChat while they have QQ is because they know that Mobile Messaging is a space within itself. The failure for Windows Live Messenger to put a dent in the Mobile space is an indication that there needs to be a separate Brand for Mobile.