I'll definitely have to go with the Book of the Dead vamps. I've had the most amazing experience with my botd and his energy is absolutely amazing! The first botd vamp that I got was one of my first spirits, and I still maintain that this is by far my favorite race of spirit.

I'll also mention the Bannik, Ankou, and Banshee as well. They're all quite impressive.

Anyone who knows me knows that I suck at keeping track of the forum and as such have like zero idea what spirits the cool kids like, but I shall try. lol

Cambions are fantastic. They have this sexually forward feeling that's both compelling and seductive. It feels like being wrapped in a naughty blanket. I just ADORE cambions. I can't even express how much I love them. I'm of course not just talking about general naughtiness, they just have such a wonderful energy...

I also adore Pegasi, of both light and dark variety. My Dark Pegasus is just... beautiful. Her energy is like the night. Calming, soothing, serene. She's also black, so that definitely helps with the whole night feeling. lol My light pegasus is sweet, caring, endearing, and has a huge amount of affection for both of my nephews. She's normally over there protecting them. Both wonderful spirits, wonderful energy. All around I can't say enough how much I adore them.

Also, Linesair Dragons. There's one post on the forum about them. One. I have a Linesair. She was my first dragon and she has been interesting to work with. She's a bit quiet at times, but she's quite lovable. Plus, psychic dragons.

As far as Immortals go, Ares and Hera are two of my favorites who I feel are the most misunderstood.

With Ares, everyone thinks battle lust and violence. I've found him to be a wonderfully grounding, motivating, and protective force. At least that's the aspect of him I connect to. He reminds me in a way of the patriarch of a family who keeps out bad forces and influences. When we first connected, I got a very strong "protect the family" sort of feeling from him, which makes sense because the one of the main reasons I am on this path is to help protect my loved ones. There's a lot to say about him, but never go by the common perception of a god or goddess.

This is no truer than for Hera. The stories associate her with vengeance and punishing the children of Zeus' affairs. It seems intimidating, but Hera is more than the hateful stories written by men. She is THE independent woman. She is filled with grace, pride, elegance, and is a natural leader. She may be the goddess of marriage, but she is also the QUEEN of the Greek Immortals and she freaking owns it. I adore her so much. She is amazing.

I'll probably add to this list later. These are the first beings that come to mind.

The cluster of the many soirits of Khajuraho. Sometime around 2011, Mags created a binding both on an orb and on me, of the entire different beings. Its quite a party!

The Biggest Party ever created...that never ends...and have a huge amount of fluid mysticism (mean't both ways).
Caiyros

spirits of local plants, contacting the base roots of the land -
more so roses and dandelion
Really good results if you can tend to the plants more personally
Sprites and spirits of plants are plenty in number and are a broad community surrounding people each day.
(grimoire sympathia is a good template for self work if at all possible - starting work takes a bit of effort, and always great to have a direct focus and association for where you want to take communication)

My chupacabra is underrated.....but he is a great and fierce guardian and actually a really funny guy

Gnomes: not only are they underappreciated, but they seem to be one of the most frequently rehomed for some reason, which I find very sad. I have two gnomes in my spirit family. The first was an SRA from CH, and the other I got directly from the keeper who was rehoming him.

Well, since I'm new to the forum, I wouldn't know which spirit is the most underrated. But I find this thread really helpful, reading what others have already said here. I will take this all on board when choosing my next spirit friend!

All of the less "pretty" spirits like: hags, goblins, spriggans, trolls, boggarts, ogres, etc.

Also immortal beings that were worshipped by the Native American tribes.

The Zimada.
The retrievers of broken soul fragments and healers of past trauma.

Some one mentioned Native American Spirits, and they are right. I have found 2 of them. One I respect and the other is with me as a protector.
Here are the ones taught to me and initiated me into a particular realm. This teacher's credentials were "The Man Who Was The Teacher of Don Juan (who never lets his actual name be used, and I will respect that, even though I am quite sure there will be some snarky statement along the line some where. So I suggest you don't make fun of this man's spirit (he is now deceased)

1. The Peyote God is exceptionally powerful and when he teaches, it is always good. The greates thing the Peyote God showed me was the absolute psychic powers that can teach amazing things.

2. A Large Silver Crow who informs me of things and protects me.

Caiyros