Ranma 1/2 - its a comedy about a guy and his dad who fell into some kinda magical spring/pond and from then on, whenever they come in touch with water, they would change into a girl (Ranma) and a panda bear (Ranma's dad). It brought a lot of joy for me back in the 90s when I was still schooling. Compared to anime release past few years, you'll probably get bored of it after a few episodes. I think Ranma has a few seasons, more than 5 seasons from what I can remember. It has a fair amount of martial arts scenes and some ecchi scenes as well! =D there are lots of things a guy could do if he is transformed into a girl =P
If you wanna try watching, you might want to consider watching some of the OVAs. There are a few of them and they are just as interesting!