There's nobody in Mass Effect that I dislike.
Miranda and Jacob aren't particularly deep, but I find them very likable.
Characters like Tali and Garus I have a strong connection to, and everyone else is at the very least(Jack and Grunt) a little bit interesting.
Some of them I don't want dead just because they intrigue me too much, and ME3 will be a better game for they're involvement(Mordin and Legion)
I think I would just do and hope for the best, but If I had to choose...
If it were real life:
Zaed(Is that how you spell it?): He's old and has lived a full life. Incidentally, he's also my least favorite character
Thane: Thane was another one of my favorite characters, but as much as I don't like it, he's going to die, saving a galaxy isn't such a bad way to go
Legion: He's not really an individual, so if he dies, it's less like an actual death and more like a concussion or minor lobotomy
Samera: Another favorite, but in a sense she's already dead. She's given up almost everything that has made her happy, I think her dying before she's forced to destroy herself even more could be considered mercy
But in game...
Tali(Maybe): Simple, love interest dying gives Sheppard a chance to develop further as a character and brings more weight to the situation. On the other hand, there's great potential for drama between her and Legion, and the Quarion war or lack thereof will have more weight with the addition of a personal connection
Jack: Not much else I can see being done with her character
Jacob: As likable as he is, he's still a token nice guy, a handicap to this day only Alister from DA:O has managed to make interesting. I think the best service his character can provide for the story is to have a tragic death
Zaed: Again, least favorite character. Cool and reasonably likable, but he pales in both categories compared to the other crew members
