Last I checked there are almost 30 different Hive Engine tribes, each with their own niche and token. While I know most of the tribes, at least what niche they are, there are some I haven't even heard of yet.
It's impossible to use and participate in every tribe, so you have likely chosen a few that you want to be part of in some way.
What tribes do you participate in, and which are your favorites?
I only participate in a handful of tribes, there are only so many hours a day you can spend. Which ones? Glad you asked!
STEMGeeks
STEMGeeks is my own tribe focused on Science, Technology, Engineering, Math (STEM) topics. I had a few goals in mind when I created the tribe.
I wanted to attract casual discussion, less formal than SteemSTEM at the time, now STEM Social. As long as it is on topic and your own work, it is welcomed in STEMGeeks.
I wanted to create a token that had very aggressive tokenomics, and did not have high inflation or heavily abused. I believe this has been extremely successful, but I don't think most understand to what extent.
Finally, I wanted a vehicle to onboard students and professors where they can participate potentially in their first crypto while talking about what they love. Unfortunately do to many circumstances and technical limitations, this hasn't been working out as much as I would have liked, but I am working on some changes to improve this.
Leo Finance
I have been using Leo since the early days of it's creation. Leo Finance is focused on Finance related content. I believe it has a unique advantage over all tribes present and future in that it is a common interest between everyone on Hive. Most tribes are a sub-group of a relatively small community. This makes it difficult to have a thriving community, Leo doesn't have this issue.
CINE
Cine is a new community created by 
From what I understand, there are some interesting developments being worked on for this community. I believe this community has a good chance of attracting new users to Hive. CINE token was built with low inflation and strong tokenomics.
Archon
Archon is one of the newer tribes I got involved in. It is a general tribe which is focused on supporting good content creators rather than a specific niche. Generally I don't put much time into General communities as I feel a community for everyone is a community for no one but I like the low inflation and unique elements of this tribe. I have a few miners and a little stake, but I don't spend too much time focused on it specifically, as many times it is the same posts I am already looking at anyway.
Proof of Brain
This is the newest tribe I have looked at. It focuses completely on proof of brain with no initial supply or other forms of inflation outside of a single token issued to the tribe's account to kick off the reward pool. Inflation will half every 4 years following BTC's strategy. It even has a 21M token limit taking after BTC as well.
While it is another general community, it is unique and I see it as an interesting experiment. While it potentially can be attractive to outside users, I see it more of a Hive community, although I'd love to see it go further than that.
While I do tag some other tribes depending on the post, I mostly am focused on these tribes. I have recently picked up a good share of CTP & Vibes miners.