I think Debbie is probably my favorite for her absolutely huge heart (it's even bigger than her mouth, but maybe not by much *g*). She is a force of nature and she loves so hard, both of which I admire her for.
I like Jennifer for her quiet strength -- she's a huge part of what makes Justin who he is. I also like that she finally had her own little romance in S5. She is a sexy lady and deserves a sexy boyfriend. ;-)
I love Mel because she's feisty and smart, she loves fiercely, she doesn't take crap from people, and she's hot, yo.
I like Lindsay in a sort of similar way to the way I like Jennifer, actually -- they both are more "ladylike" characters, but they have cores of steel. I always enjoy when Lindsay tells Brian like it is. (He really needs strong people around him to do that -- Lindsay, Debbie, Justin.)
Daphne is lovely and fun, and I wish she'd been on the show more often.
Cynthia is awesome, and I wish she'd been on the show more often too. :-)