I feel like the monks are kind of hard to convince to do... well, anything. They don't respond all that well to bounty flags and tend to crawl around the settlement while uttering "ooooh" and "ommm" sounds. Which is fun, but still.
For me, the most fun unit is the cultist. I've always had a blast spamming them, perhaps even more so in scenarios that heavily encourage healers/paladins.