Hmm, it's a tough choice between Fai and Kurogane, but I'd have to say Fai wins out in the end. If only because I keep winding up as him on Tsubasa quizzes (and Mokona, too! They're both so cool!). That and I like Fai's personality. But I like Kurogane lots, too! They're both great! (And so is Mokona!)
As for Syaoran and Sakura, definitely Syaoran. But that might just be because I've only read volumes 1-4 and Sakura spends most of her time asleep. But I do like Sakura, too.