Best SMS App?

I know this has to do with apps, which is another forum category, but I would just like to hear from this side of the story. Which SMS app do you think is the best?

I like using Kik Messenger, it's fast and reliable. But them there's WhatsApp, Facebook Messenger, Google Hangouts, and iMessage. And there's even more I'm too lazy to list. So tell us which ones you use!