It can be hard to find that go to messaging app that you absolutely love. There's nothing wrong with the standard messaging app within Android, it's just boring. Hangouts has done a decent job at replacing the stock messaging app for many people, and with the addition of emoji and the link to gmail, and google+, hangouts provides a nice substitution to the everyday SMS app that comes with your device. What if you don't care to use Hangouts as your default SMS app though? Maybe you like some of the features of having Hangouts do all the work, but you would rather separate Hangouts and messaging. So, what's a person to do?
You could check out Sliding SMS(CM Messaging) instead, which is a decent alternative to having Hangouts act as your default. It has a similar sliding style to it so you can slide back and forth between your list of contacts that you're messaging and the actual conversation going on between you and each one, and it even has the reply from status window feature that is synonymous with Hangouts, and it comes with a snappy interface that's easy to use and ultimately a less bland solution than stock SMS. Among the features already listed it also supports breathing notifications, so when you get message notifications in your status bar the icon will fade in and out to give it a breathing effect. It's more of an aesthetic trait but it can become useful as it can serve to catch the eye if you have your phone on silent.
Sliding SMS also supports themes and color schemes for the message boxes, so if you like to customize, you shouldn't be disappointed. The best part about all of this of course is that Sliding SMS is free, and the one man dev team is keen on providing as much support as possible to keep the app running smooth. If there is an issue they seem to respond quickly and make attempts to fix whatever problems may pop up. You can also show or hide contact avatars, which could come in handy if someone's contact avatar is nsfw. It also has the pop up reply feature so you can quickly send a message from where ever you are on the phone without having to switch to messaging. If you want to give Sliding SMS a try, you can grab it for free from the link.