My rankings.
1. Garrus: He's f***ing Garrus
2. Kasumi: While she's lacking in dialogue and interactions, she has an awesome loyalty mission and the dialogue she does have is great.
3. Mordin: He's the very model of an awesome teammate. Also, surprisingly deep when you listen to his thought process. Great loyalty mission, especially since it makes him question his own actions a bit.
4. Thane: Actually the best romance storyline (on noes im dying). Also a great character, sucks that he's not acquired right away.
5. Tali: Definitely improved from ME1, shows a lot of individual growth. Very good loyalty mission (;_;).
6. Grunt: Not as good as Wrex, but provides a much more interesting look at the Krogan people. Has some good moments, loyalty mission was completely underwhelming.
7. Jacob: Haters gonna hate. Personally, my favorite loyalty mission, such a messed up situation and has a great moment for Jacob. Without, he'd probably be lower.
8. Miranda: Despite her claims of perfection, is the perfect example of complete average. Average character, average storyline, average loyalty mission (cool interrupt, though, at the beginning).
9. Zaeed: Great loyalty mission, few nice lines of dialogue, but rather bland for the most part.
10. Legion: Great concept, didn't like the loyalty mission all that much, execution was pretty flawed and not enough time in your squad. Still "Geth do not intentionally infiltrate" is one of the best moments in the game.
11. Samara: Your t**s can't save you from being a general boring character. She has a great loyalty mission, except the funny part is that she's hardly involved in it compared to the other ones. So I can't really call that a plus for her.
12. Jack: I can deal with the "bad girl" image, but Jack comes off as so friggin' forced that it comes off as incredibly fake. Maybe romancing her makes her more interesting, but otherwise she's generally terrible. Also, that outfit looks more like it should be in FF or something.
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TheRock ~ Slow dramatic zoom-pan. Doesn't phase the hooded man.