Really?
Is it your school or your club advisor that wont let you watch anything past pg-13.
Our anime club allows anything but hentai, we've watched Shuffle, Chobits, Midori Days, and other things with nudity, language, blood, ect. We might watch Elfen Lied this year. We just have to get parental forms signed for each member at the beginning of the year. You should ask you advisor if you can change that and do parent forms, just make it clear everything you watch will be in decency and not pornographic.
I'm really not sure on pg-13 anime, but I can give you some advice on what anime in general not to watch. Stay away from anything thats on TV or has been on TV (Naruto, Bleach, Cowboy Bebop, Trigun, ect...) That way you watch something no ones really seen. Hmmm.... I DID think Scrapped Princess was a really good anime and it would be appropriate for your club, you got your bishi, your action, your magic users, your robot-creature things, more creature than robot. Escaflowne was another good one.