I also love Work It Out!, it's so unique in her discography and I personally think that her voice fits it perfectly!
But I love UNIVERSE as a whole, not a single song I really dislike. That never happened before, there always were one til three tracks I totally dislike on her albums. Even Stay is pleasant for me, even though I normally don't like this kind of songs.
That's the reason it became my favourite album by her!
I'm just missing Hashire! on it, such a great song! ;_;
Edit:
Top 20 Requested Karaoke Love Songs
1. Sakamoto Fuyumi – Mata Kimi ni Koishiteru
2. EXILE – Lovers Again
3. MONGOL800 – Chiisa na Koi no Uta
4. Koda Kumi – Ai no Uta
5. Shounan No Kaze – Junrenka
6. Ozaki Yutaka – I love you
7. GReeeN – Ai Uta
8. Koda Kumi – Suki de, suki de, suki de
9. Akimoto Junko – Ai no Mama de
10. Kato Miliyah & Shimizu Shota – Love Forever
11. Arashi – One Love
12. Arashi – Love so sweet
13. Superfly – Ai wo Komete Hanataba wo
14. Ishihara Yuujirou & Makimura Junko - Ginza no Koi no Monogatari
15. Kuwata Keisuke – Shiroi Koibitotachi
16. Fujitani Miwako & Ouchi Yoshiaki
17. Saito Kazuyoshi – Zutto Suki Datta
18. SPEED – White Love
19. DREAMS COME TRUE – Osaka LOVER
20. Matsuyama Chiharu – Koi
Source: Barks
Thanks to Angel_Angelic at JPM for posting.