Hey! I'm using GO Keyboard which as the Best app of 2015 on Google Play. It has big variety of different stickers, that makes chatting more fun. Just try GO for free and you will love it.
Android: https://play.google.com/store/apps/details?id=com.jb.emoji.gokeyboard&referrer=utm_source%3Dstickershare%26utm_medium%3DHyperlink%26utm_campaign%3Dsticker
iOS: https://itunes.apple.com/app/apple-store/id916226412?pt=114123925&ct=gokeyboard&mt=8