In another Bigglobe Poll reported by Crunchyroll Japanese fans named the best "underselling" anime. Here is the list:
1 (320 votes) Kaichou wa Maid-sama! (Maid-sama!)
2 (251 votes) Taisho Yakyuu Musume (Taisho Baseball Girls)
3 (239 votes) Chihayafuru
4 (218 votes) Kure-nai
5 (251 votes) Kamisama Dolls
6 (178 votes) true tears
7 (157 votes) Ikoku Meiro no Crois?e (Crois?e in a Foreign Labyrinth)
8 (135 votes) Kill Me Baby
9 (132 votes) Kuragehime (Princess Jellyfish)
10 (114 votes) Seirei no Moribito (Moribito)
11 (111 votes) Sora no Manimani
12 (108 votes) Shiki
13 (102 votes) Sofuteni (Sofutenni)
14 (97 votes) Hourrou Musuko (Wandering Son)
15 (96 votes) Sasameki Koto
16 (95 votes) Nabari no Ou
17 (82 votes) Neko-gami Yaoyorozu (Cat God)
18 (80 votes) Shukufuku no Campanella (Blessing of the Campanella)
19 (76 votes) Natsu no Arashi
19 (76 votes) Aoi Hana (Sweet Blue Flowers)
21 (71 votes) Kenkou Zenrakei Zuieibu Umishou
22 (70 votes) Skip Beat!
23 (69 votes) One Outs
24 (65 votes) RD Sennou Chousashitsu (Real Drive)
25 (64 votes) Wagaya no Oinari-sama (Our Home's Fox Deity)
25 (64 votes) Goshuushou-sama Ninomiya-kun (Good Luck! Ninomiya-kun)
25 (64 votes) Bokurano (Ours)
28 (56 votes) Jewelpet Tinkle
29 (54 votes) Shikabane Hime (Corpse Princess)
29 (54 votes) Itsuka Tenma no Kuro-Usagi (A Dark Rabbit Has Seven Lives)
31 (48 votes) Noramimi
32 (45 votes) Potemayo
33 (44 votes) Yoku Wakaru Gendai Mahou (Modern Magic Made Simple)
34 (42 votes) Myself; Yourself
35 (41 votes) Ghost Hound
35 (41 votes) Simoun
35 (41 votes) Sketchbook ~Full Colors~
35 (41 votes) Mouryou no Hako
39 (40 votes) Pita-Ten
40 (38 votes) Magikano
41 (37 votes) De Gi Charat
42 (36 votes) Kidousenshi Gundam Age (Gundam Age)
43 (35 votes) Bounen no Xam'd (Xam'd: Lost Memories)
43 (35 votes) Casshern Sins
45 (33 votes) Hatenkou Yuugi
46 (32 votes) Umi Monogatari Anata ga Ite Kureta Koto
47 (31 votes) Hitohira
48 (29 votes) Saraiya Goyou (House of Five Leaves)
49 (27 votes) Souten no Ken (Fist of the Blue Sky)
50 (20 votes) Boys Be?
Anything below 20 votes didn't make the list.
I would have to say that Chihayafuru and Hourrou Musuko (Wandering Son) are the top two for me on that list. I think Hourrou Musuko (Wandering Son) wins for me, since Chihayafuru is getting a 2nd season despite low sales. From what I have gathered, the real purpose of the anime was to drive up sales of the manga and that
did happen, to the tune of a 10-15% above the previous volume for
each volume since the anime started. If I recall the articles correctly (and I am not going to go and dig them up) it was something like a 12% increase in first week sales for the first one, 10% for the 2nd, then about 15% for the third. If you do the math, with pre-anime sales as 'X' the first volume after anime sold at around 12% above, so that would be (1.12X). Then the next volume would look like this:
1.12X + (0.10(1.12X)) = 1.12X + 0.112X = 1.232X
And the next like this:
1.232X + (0.15(1.232X) = 1.232X + 0.1848X = 1.4168X
So they have a 40% increase in first week sales since the anime started. That is pretty darned good, especially for a manga that sold relatively well already! It is still miles below the performance of the big Shounen Jump titles, but it is still pretty significant!