Piip Messenger is the latest cross platform messaging client to come to BlackBerry 10. The interesting part here is that the app is free and cross platform. In this case it is also available on desktops including Windows, OSX, and even Linux. In short it is available practically everywhere including a web messenger option. They have group chat options along with the ability to send photos and files along with contacts and location. Keep in mind it uses your phone book to get your contact list.
Check out Piip Messenger and let us know what you think!