She's just the most awesome in the trailers, and so far in the series she's just quiet and intelligent. She's also in the middle of the entire plot. I think she'll likely be the most plot-heavy of all the characters. She seems to be tied into White Fang, somehow involved with Schnee Dust Company, and may or may not be connected to Junior and/or Roman (depending on whether that was her on the tablet in the Yellow trailer.. There's also a theory I have which would tie her into yet another major plot element.
I'm always a fan of "minor" characters, especially when they make the best of their limited time. And when the only line a character has had so far is quite possibly the funniest, that goes a long way for me. Plus, he also had an awesome landing. I hope he gets some good content and they continue to make the most of it.
Going with another non-main character here. I love how she is just the exact opposite personality of Weiss. Even though she has had tons of success, it almost seems like she shrugs it off. She obviously knows how good she is, but I think she sells herself short a lot. She seems as if she's not the "cool" person, but rather the sort of odd duck who just so happened to actually find success and have fame and fortune thrown all around her. As Ruby would say, she just wants to be "a normal girl with normal knees".
Going back to the main characters. Other than Blake, nobody struck me as more interesting than the rest just from the trailers. But after the start of the season, Weiss has taken me by surprise. Not at all the personality I expected, but her "crabbiness" looks like it is heading toward an amazing and emotional character.
Just so adorable.