I would highly recommend Trigun. It has a perfect mix of action and comedy. It was the first anime series I started collecting, and it remains my favorite to this day. I'm pretty sure it isn't rated for over 13...there is a little blood, one scene of nudity (very brief, and it was from behind), and very few curse words. And in my opinion, it has one of the best story lines in anime. It does get pretty dramatic towards the end, but the comedy pretty much remains throughout.