I found 奇麗 in the JLPT 4 list (Section 11). I've never seen きれい written this way before. Only as 綺麗. So I asked my Japanese girlfriend about it. She also has never seen 奇麗 before and even said that it's weird.

However, doing a google search for it I came across this:
http://detail.chiebukuro.yahoo.co.jp/qa/question_detail/q139444933

Here, some posters say that 奇麗 is the normal way of writing it and that the 綺 in 綺麗 is an archaic way of writing it and is not in the jouyou kanji. They said that some people still write it this way though because has a prettier feel to it.

What is everyone else's experience with this? In what way would you recommend writing it?

Yes, 綺 is not in the jouyou kanji. So, if you are writing an official document or business letter, you should use 奇麗. But if you are writing your diary, personal letter or a novel, using 綺麗 shows that you are more refined and educated.

Thank you :)