Well I've quickly developed a love for harem anime, and in the past month I've run down a long list of harem anime, and feel like I'm out of options.

I like harem anime with action, story and romance, not particularly slice of life harems.

I also really like tsundere characters!!!

I've watched:

Hidan no Aria
Sora no Otoshimono/Forte
Hayate no Gotoku (All seasons)
Zero no Tsukaima (all seasons)
Shakugan no Shana (all seasons)
Date a Live
IS: Infinite Stratos (and season 2)
Kore wa Zombie desu ka?/Of the dead
Campione!
Clannad /after story
Omamori Himari
Highschool DxD/New
Highschool of the Dead
Outbreak Company
Sword Art Online
Btooom!
Accel World
To Love Ru (all seasons)
c3
Asura Cryin' (all seasons)
Sekirei/Pure engagement
Hagure yussha no estetica (and OVA's)
Demon King Daimao
Oda Nobuna no Yabou
Golden Time
Strike the Blood
Rosario + Vampire/Capu2
OreImo
Princess Lover!
So, I can't play H?
Mayoi Neko Overrun