Love Hina

One of the best mangas in my opinion, it's about a down-on-his-luck man named Kietaro, who made a promise to his dream girl to make it into Tokyo U.
Well, he failed the entrance exam three times, going on his fourth when he gets kicked out of his house, and becomes the manager of a girls dorm. All of the girls love to kick the shit out of him, because he (luckily) always accidentaly slips in on them dressing, or taking a bath. He falls in Love with one ofthe girls there, and that's when it gets wackier.

I'm not gonna say anything else, so go read it yourself!