Ranma 1&2

If you've got a playful and slightly perverse sense of humour, I would highly recommend the Ranma books!
Water is the key to all the mischief played out here, one splash of cold water and half the characters are turned into someone of the opposite sex, a giant panda, cat, duck, pig the list goes on... Only hot water can reverse the change. The unfortunate titular character, along with changing sex constantly, also seems to be in the habit of picking up fiancees too!! He is officially betrothed to Akane, a rather hotheaded tomboy, both are too stubborn and unwilling to admits their real feelings for each other.

I've really enjoyed this series because only here would I find a giant panda using plackards to make wry comments and in the most unuseful way possible either to mock or warn his son of danger. I still can't get the picture of bra-fu being used on an old pervert to great effect!!!