Mine would be..
1. Clannad + Afterstory (STUPID mistake of watching during my exam period...)
2. Infinite Stratos (Gotta love the Harem hehehe )
3. Highschool of the dead (Boobs and zombies, cmon... what is not to like?)
4. Aria The Scarlet Ammo:Hidan No Aria (A very good Tsundere and action packed)
5. Chrome Shelled Regios (I love a good Harem with the male protagonist is extremely powerful)
I can list way more, this is just a few. I also like other animes with Harem and romance that nobody has listed yet, such as Maburaho, Girls Bravo, and Rosario + Vampire