>>3121340Its hard because like the best harems are built up gradually, I don't know about just going into a series to build up a harem you'll end up with a bunch of fujocore whatever. Free, Yuri On Ice, Haikyuu. Prince of Tennis or Hetalia if you want to go a bit older though they've fallen from favor. Maybe Ouran if you can accept the presence of a female lead. Jojo's Bizarre Adventure. I just finished Osomatsu-san and that was kinda popular with fujos. If it can sustain a thread on /cm/ its probably got some decent husbandos.
Its better to look at series which sound interesting to you and then pick up husbandos passively.
My husbandos came from
-7 Seeds (josei manga)
-Amnesia (VN and anime series but the anime got shit reviews)
-Baccano (anime)
-Berserk (seinen manga and anime)
-Black Wolves Saga Bloody Nightmare (trashy VN)
-Cheese in the Trap (Korean webtoon)
-Dengeki Daisy (shoujo manga)
-Fate/ series (VN and anime series)
-Gintama (shounen manga and anime series)
-Hakuouki (VN and anime)
-Hana Yori Dango (shoujo manga, anime and tons of live adaptations)
-Kamisama Hajimemashita (shoujo manga and anime)
-Nana (shoujo anime and manga series)
-Ookami Shoujo to Kuro Ouji (shoujo anime and manga)
-Psycho Pass (anime)*
-Skip Beat (shoujo anime and manga)
-Tokimeki Memorial Girls Side III (VN)*
-Vagabond (seinen manga)
-Zero Escape (VN or adventure game)*
I also want to boot out someone to make room for Zen from Mystic Messenger (VN). I have runner up husbandos in Sakamichi no Apollon, Oooku, One Piece, Nodame Cantabile, Umineko no Naku Koro ni, Durarara, Fushigi Yuugi, Cowboy Bebop, Samurai Champloo, Gekkan Shoujo Nozaki-kun, Phoenix Wright, Chumo Once Again, Fruits Basket
Have a gallery of anime rec charts:
http://animu-mango.wikia.com/wiki/Specific_Recommendations 
