[Nyx]

I'll try (even though I don't watch a lot of harem >.<):
Kanon
Boku wa Tomodachi ga Sukunai
Mashiroiro Symphony: The Color of Lovers

Or you could check out School Days. It's hands down - the best harem ever. Being 100% serious. Heh.

I can't really think of any more

I should have added this into the Thread, but with School Days, its only 2 girls, and I prefer 4 girls, as it adds a comedy element in my opinion.