Wow, when I first started to answer this post, I was going to say that I like ponies that's pose is looking up to the sky like they are daydreaming (Skyflier pose, baby Cotton Candy Pose, even Seapony Wave Jumper pose, G3 Diva Pose) but then when I looked at some others looking to the sky, like Mimic pose and G3 Crystal Lace, I realize I don't like those... maybe it has to do with their legs being bent? I seemed to like the ones that have their legs straight... that seems to be a more common thing that I like.... hmmm I never realized that before... *excuse the rambling*
and I especially like ponies with Freckles (like Baby Blossom, Applejack, etc) ...
but I prefer bold colors like Masquerade, Pepperberry, Scootaloo, Silver Rain, ComicCon 2007, etc... I do love neon hair too!
Mostly, I just love them ALL! yes, all!