Kare Kano (Or Kareshi Kanojo no Jijō, or His and Her Circumstances)
For all the wildness, crazy characters, and Anime wackiness it throws in, at heart it's actually a very sweet, believable story of a high school romance, complete with heartwarming ups, and trying downs. Just be warned that the last few episodes don't really resolve anything, and are nowhere near as good as the rest, and if you want to read the Manga that continues the story, it will pretty much give you cliche, overwrought drama that's actually kind of painful.