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Asking this isn't the best idea, because a lot of women aren't really capable of giving you anything but vague answers. I mean look at the two that have already posted, it's just vague, umbrella, broad-brush bullshit because they don't wanna tell you what they're actually attracted to in case it makes them look bad.
Anyway I'd probably say height. If a guy's 5' 4" a chick's certainly gonna be noticing and disliking that, whereas a 6' 3" dude's obviously gonna be more eye-catching (providing he's proportioned well, though a disproportionate tall guy is still more attractive than the 5' 4" guy).