In no particular order:
Hazeri
He's nice, kind, detailed, and has a thought out personality. He feels well rounded, plus, I have a soft spot for characters that actually try to be nice, because so often it feels like there aren't a lot of those (Even if it is just because the jerks tend to be more vocal)
Igam Yute
The flirts-with-everyone assistant/bartender with the heart of gold. He not only has enough of a backstory to do an HBO series on, but he's been around long enough and interacted with characters often enough that much of this backstory actually took place on the station and involves characters you can interact with.
The fact that he flirts with everything that moves works in his favor by essentially giving him interactions with many different characters aboard the ship
Nasir Hakim
Even though my CHARACTER likes him, I OOCly think he's kind of a jerk. BUT, what sets him apart is that unlike so many of the other jerk-y characters on the station, he's not one-note. When he is angry or bothersome it usually has a rhyme, reason, and specific situation that triggers it, and you can actually discuss things with him, even if he is somewhat stubborn. Plus, he's not always like this, sometimes he is nice He's well rounded and while I don't know what it is, specifically, he clearly has a backstory of somekind.
Lachina Green
Okay, so, I barely get to interact with Lockie at all, for some reason, even when I work Medbay. But... She's clearly a well developed character and whenever I overhear her saying or acting a certain way it makes me wonder what's the story there, why is she doing this or that, what caused her behavioral shift lately, etc. etc. These are marks of a good character.