You left out the resteem bots. Similar to the vote bots, but they resteem instead of (or as well as in some cases) upvote. I think they form the potential for a very interesting solution to a common problem. Namely, that categories can't be followed in a feed, only people.

A resteem bot that was and, say, resteem-politics, and just auto resteemed every post with that as a first tag could then be followed to always follow political posts regardless of who made them. I'm about 75% done with such a bot, just have to shell out the cash to make a few sub-accounts and start testing it.

Figured I'd start small, a few high profile categories, and then move up from there through a few votes on which category to do next.