My favorite personally is steemnow by @penguinpablo. It encourages me to strive to that next level of reputation and shows me how much voting power I have in the tank. It's a simple app, sure, and maybe not as well known as some, but it's my fav. I also like Steepshot a lot, it allows me to easily participate in photo challenges and share small pieces of me. Finally, I have to give honorable mentions to blocktrades and eSteem. eSteem is the only mobile app I have that I can dictate notifications for and at the same time, put up some snazzy posts. It's not Steemit...but it's close.