For me personally:
Cyclostomates like Lampreys/slime eels, particularly with slime eels you have so many based traits like having multiple accessoric hearts (consisting out of smooth muscles), having no cerebellum (an important part of the brain for motoric skills being there in every other vertebrate, in lampreys it's existent but without the characteristic Purkinje cells, motoric skills aren't important for them anyways due to being scavengers and parasites), no jaws, etc.
Particularly with slime eels people still don't know whether they lost their more vertebrate-like features secondarily or never developed them in the first place. And lampreys often have unique life cycles/larvae.
Simply very based animals that serve as the sister taxon to all gnathostomates (animals with jaws like us, jaws are btw derived from the gill arches and this is how the very based pharyngeal jaws developed too). And funny: Agnathans are a paraphylum (common ancestor) if we take ourselves out, but strictly speaking we as gnathostomates/jaw-carrying animals are agnathans/jawless animals because having a jaw is a derived/apomorphic trait (we simply belong to them).
And apart from that the cartillagous fish (like rays/chimaeras/sharks). They survived over millions of years, they deserve to rule in the future too.
Very based, they are furthermore more related to the birds (which are their recent sister taxon) than to any other animals, they are the last remnants of the diapsid archosaurs (along with the birds as the only living theropods/dinosaurs). They have completely unique sensory systems too.
But the tuataras are based too. They might look like ordinary lizards, but they are the last living rhynchocephalians/sphenodonts which were the sister group of the squamates (lizards/snakes), they have three eyes too, unique genitalia, live together with birds, only become sexually mature after decades and are threatened due to climate change due to having a temperature-dependent sex determination like chelonians and crocodilians (a lack of heteromorphic sex chromosomes/gonosomes).
