They're all great, so it's hard to choose. But for me, it has to be Dapplr. Hive deserves a good app, and given how much time we spend on our phones every single day, I think it's key to get more people into the Hive.
A sleek, pretty, and workable app for the millions of future Hivers to come, with all the functionality and power of the community at the tap of your fingers :-D