The closest I've gotten to writing a Human on this site is a Miralukian. So, here we go:
Miralukians are a fun species to play as. Seeing everything through the force is kind of tricky narratively. But it's fun.
Columi are hard to write, because they are as a species substantially smarter than most other things. It is tricky to write a hyper-intelligence being. That being said, Olom is my best villain.
Droids are decidedly not human, and I do enjoy playing them. They aren't aliens, so I'll leave it at the fact that a droid's nature (and it's deviations in that nature) is often compelling to write.
I have one Morseerian who I don't use as often as I should. He's fun. Not being able to breath in most atmospheres is a challenge in PVP, though.
I have one character who is a weird mutant Hutt/Xa Fel hybrid clone thing. I made him mostly out of snark, and have yet to do anything fun with him.
Sugar is a Smoke Demon. he is super spooky, from his fangs to his wingtip shoes.
Frankly, the one species archetype I haven't played around with yet are insects and aquatic species. Both of them work.