Byteball looks very polished. The option to do both public payments (bytes) as private payments (black bytes) is very handy, although bytes and black bytes are two different tokens.

The distribution scheme is very unique (you basically need to tie your Bitcoin wallet with BTC balance to your Byteball wallet during the period of drops) and ensures an active and distributed crowd of users/hodlers.

Together with Nimiq, I consider this one of the challengers to Bitcoin.