WHAT A GOOD QUESTION NICE OMG!!!!!! i went through all the costumes on the wiki in case i forgot any good ones but i think i still have to go with the one she has on during the final judgement thing with yue on the tokyo tower (this one http://ccs.wikia.com/wiki/The_Pink_Cape_costume)! its cute and also the first one i thought of when you asked. what about you??

also looking through the costumes i also remember that i loved the ep when syaoran was being controlled by the threads!!!!! lol i love every episode