I like to see new riak_core applications being made. For the most part it's a pretty clean framework to bootstrap something with.

I have a current particular interest in riak_core over the top of a pile of disk_log because I want something Kafka shaped, but where topics are cheap, and sloppy-leader-esque behavior is the default without destroying data. Optimizing for availability over everything else and guaranteed delivery of all ACK'd messages put into the system if the end of all logs have been reached (via continuation).