16. Chloe O'Brian (24)
I think Chloe is one of the most consistently funny characters on the show, and I also like that they took the character of this nerdy little computer geek and made her into a dynamic and multi-faceted character over the course of six seasons (seriously, Chloe surviving the series has gotta be one of the biggest shockers ever, given how many characters have a penchant for dying around Jack).
Chloe has always been a supporting character. That's not a bad thing, but it just means that, for the most part, she doesn't have the kinds of main storyline that other characters would, and those are the storylines that better work into long write-ups. Basically, Chloe is a background character (as you can tell in season three) that rose to stardom because she was so quirky and intriguing...and probably because there were so few returning characters for season four that she got thrown in there and became the legend that she is today. She's like the Benjamin Linus of the 24 universe, in my opinion, in that there's no way she was ever intended to become as big a fan favorite as she is, yet her slightly abnormal personality just clicked with a lot of viewers, resulting in greater screentime and even more fans.
Season three, she was the weird, socially awkward analyst, which was a change of pace from earlier seasons which had analysts that seemed way too confident in themselves, or died before they could really establish themselves as quirky. Early on, Chloe's only reason for existence seemed to be Chase's baby, but that was a plotline that faded quickly because of how stupid any plot relating to Kim usually is. She came back for season four and continued to be awesome in several instances from then on, always having this pissed attitude towards her colleagues that managed to be comically because it seems like everyone has that one co-worker like Chloe who is just unintentionally hilarious and annoying, but they don't realize it even for a second. If you don't recognize this person at your workplace, you ARE this person.
She had some awesome moments, like tazing a guy in the neck for flirting with her (SUCH a bad flirt too), running away from an assassin who was looking to up his kill count to four in episode one of season five, and of course, grabbing an AK-47 and blowing a bad guy away while he was trying to ram her car. Hell, in season eight, after many seasons of violating protocol in order to help Jack while on the run, she actually showed a new side to herself when she was promoted to head of CTU and had to hunt him herself. Yeah, she was bad at it and wound up getting sleeper-held, but the point is that Chloe wasn't a one-trick pony. And all of this happened while managing her personal relationships with those around her. Despite being awkward, you could see the emotion Chloe felt towards each and every person she worked with. She secretly had a crush on Jack, she banged Spenser and was pissed at him about it later. She was friends with Edgar despite not being interested in him the way he was to her. She even had her marriage to Morris which came out of left field for three seasons, resulting in a baby that was never mentioned again after season seven. All of these interpersonal relationships really helped us get to know Chloe, and it basically turned her into an avatar for the viewer at home. Because let's be honest...most of us who watch these shoes are just like Chloe...or at least we used to be. Not good in social situations, maybe not the prettiest person ever, but not ugly by any means...I think that's another reason why she's so popular...because she just clicks with the fans, and I like that.