49 Eternal Sweeper
I really liked Eternal Sweeper -- the costume, the concept behind the character, and also the sets, staff fighting and ninjitsu. Staff was one of those sets that seemed a little lackluster on a brute (or a scrapper, I believe) but really shined on a stalker. Eternal Sweeper was deadly with her broom.
This was one of the characters that I decided on Sept 2nd that I had to get to 50... and then it took me almost three full months to accomplish it. I got her to 50 in the last few days before the end, and didn't really get the chance to play her very much at level 50. But I had played her an awful lot on the way up so that didn't matter so much.
This was only my second level 50 stalker, but both were a lot of fun to play. I'm sure I would have made more. I wanted to give Kinetic Melee a shot on a stalker, it was supposed to be really awesome on them too. But alas, no time.
But I'm really glad I manged to play Eternal Sweeper to 50, she was among my favorite characters.