Raven didn't care much for nicknames. Seeing couples give each other pet names made her uncomfortable and set her teeth on edge. She was so used to being called by the name she was given; why would a person want to be called something other than that? But, regardless, they were bestowed on her anyway.
After the incident with the T-Car, Raven had taken to spending time with her metal teammate in the garage. It didn't slip out often, in fact she could count the number of times it happened, but the first time it was said she didn't know how to respond. Over the years she grew into it; to this day, Raven is the only one besides the T-Car that Cyborg calls "Baby Girl".
Starfire was always the one to give affection without prompting. So, naturally, Raven was a little out of her depth when the only other girl in the tower was the opposite of her. She tried, though, going on numerous shopping trips, trying to convey that she cared. They had been walking through the tower one day, and Starfire had gotten some idea, and began to pull her along. After that, "sister" was associated with her as well.
Robin was almost as bad with nicknames as she was. She tended to think it was along the lines of this: Batman kept his charge in line with a firm hand, and wouldn't allow rule breaking such as that. But only when she really needed it, like when her powers have caused the windows to break for the fifth time that month, does he make her a cup of tea and present it to her with a smile and a "Chin up, purple eyes."
Beast Boy, on the hand, never seemed to have an issue with nicknames. She knew that he and Cyborg had plenty between them, but he only ever used one for her. "Rae" was his alone, and it took a few years to notice that the others never used it. That name could present a lot of things; that he was worried about her, wanted her to come do something with them or him, or simply because he wanted to get her to smile.
Years later, after a long day of fighting, she and Beast Boy have been left alone on the roof. He staring at the stars above, complete oblivious that she's been staring at him for the past few minutes. He starts to ask a question with her full name, and she's surprised that it slips out.
"No, tonight it's just Rae."
The smile is all she needs to know that sometimes not all nicknames are overrated.