Everyone have his/hers favourite volca, for me it is the Drum.
1. You can use it as a standard drum machine for a simple setup
or
2. You can fiddle with every sound (there are 6 parts), in many, many ways. If you know even a bit about analog synthesis - this will be a fun process. After you will arrive at the set of 6, you can than sequence them and save your preset. And than - you can chain patterns!
The waveguide effect is something interesting. Not very easy to use, it can be a bit unpredictable at the beggining, but - well - you can arrive at interesting delay/repeat/echo effects with it.