I liked Sawyer because he did what he wanted...not what he was expected to do. Then he got kinda soft.
Jack is too symbolic of the ''hero'' and Shannon DIED. Haha Serien. 
But yeah Kate was allright, at least she has the capability to kill.
My favorite might just be Anna though, she was a cop and she has some attitude. Plus SHE killed Shannon.
(and yes, I really think the two monsters were different. The big one makes different noises too! Made that wierd ratcheting noise)

Bringing Jedi Closer To Extinction