I've always liked the space orks from the Warhammer 40k universe. It's like a bunch of English football hooligans scourging space.
I must admit i've also started to really take a shineto the Ferengi after I rewatched star trek DS9, pure capitalism at it's finest!
The Daleks. So science fictiony. Cyborgs.
My favorite would have to be the humans. That's why I'm studying them.
The builders of Ringworld, our fore fathers. There was also an aquatic alien species in that series that each individual was near enough ro human intelligence but they could form a telepathic chain that amplified intelligence. The problem is the few who could do it were feared and reviled by the normies even though these specials brought them from being scavengers to multi world explorers.
Wang's carpets. Two-dimensional carpets of algae-like stuff that communicate by touching and their touch simulates six-dimensional world and interactions.
Can be found in Diaspora by Greg Egan.
I can't remember the name of the species, but The traeki from David Brin's Uplift books there are a race of animal-intelligence ring-shaped organisms that could 'stack up' to form a sapient whole. An individual consisted of a particular arraignment of rings, and adding or removing any too many effectively created a new person.
Rigelians, they actually enslave their males!
rule of acquisition 190 - hear all, trust nothing.
i have no idea what my favorite is but ferengi are definitely up there