i use trillian, its a multiprotocol i.m client that supports AOL,Bonjour,Google talk (hangouts), ICQ,IRC,Jabber/XMPP,skype,VZ,windows live messenger,yahoo! messenger, and facebook.
If your looking for one that has all mobile messaging apps in one (such as whatsapp,kik,chaton, etc etc) im afraid your out of luck, as most of those apps dont have apis for third parties to work with.
But i still prefer good old fashion texting. Dont need 1000 different messaging apps, and everyone can do it