I've only watched bits and pieces of it really so I can't really judge. It hasn't finished yet but I imagine it's going to be one of those inconclusive ones that heavily hints that female lead will end up with him.
As far as actual harem endings go, the only one I can think of is the To Love Ru series but I can't be sure of that since I've only seen bits and pieces of it as well. Kanon is a big fan of the series though.
As for inconclusive endings...welll there's loads of those . I recommend:
Boku wa Tomodachi ga Sukunai
Denpa Onna to Seishin Otoko
The World God Only Knows (<= He might enjoy this one a lot)
Kore wa Zombie Desuka?
And ofcourse, the infamous To aru Majutsu no Index series.
There's something I'd appreciate your help on. A friend of mine is looking for a harem anime with either a harem end or, at least, a harem where none of the girls get their hearts broken (i.e. so an inconclusive end could work too, lol). I'm not a big harem fan, and you probably watch a wider range of anime shows than I, so any recommendations here would be appreciated.
One show I did think of though is Strike the Blood. But I haven't followed that show in a while. Have you kept up on it? If so, can you tell me if there's any totally set romantic pairings in the show yet, or is it still harem?