Messaging, voice and video calling apps: So many of them but which ones offer the best cross-platform experience?

https://lh3.ggpht.com/Wstm2-gjhgAc3kLAY43yN0UHS3iBKwyRbQARYpxiilp6A0i96X6JNhluBgjOs_RaFkg=w300-rw

Viber, Skype, WhatsApp, Google Hangouts, FB Messenger, Kik, Snapchat etc. Certainly you can't have it all. If you shorten the list what would it look like and why?