I agree and it sounds like fun, so here goes...
For most of the seiyuu I like (female and male), their distinctive voices are the first that catch my ears.
Kobayashi Yu's
![Bliss :bliss: :bliss:](/styles/images/smilies/onions/af48944b.gif)
wacky performance of the M onna Sa-chan (Sarutobi Ayame) in Gintama and Fairy Tail's Daphne (mad scientist creating a "dragon" using Natsu' power) and how she turned serious yet still maintaining a playful side as Mei-Ren in Dance in the Vampire Bund really reeled me in.
![Big Eyes :bigeyes: :bigeyes:](/styles/images/smilies/onions/baa60776.gif)
Noto Mamiko, Nakahara Mai, Hirano Aya, and Ohara Sayaka are very versatile. Finding them in much of the wide variety of anime I like, and in really good roles, too, isn't so bad, either.
Kugimiya Rie, of course, for ToraDora and the rest.
![Shinies :shinies: :shinies:](/styles/images/smilies/onions/074.gif)
I do find Yuki Aoi's take of the somewhat "tsundere-like" roles very refreshing.
I'd really like to see more of Kano Yui.
For the male seiyuu, it's their distinctive voices, styles, and sometimes the type of roles they take, especially in comedy. Serious is easy, but how Fukuyama Jun (Nurarihyon no Mago, for one)and Sugita Tomokazu (Gintama) changes from one to the other within one anime (betsujin mitai) is amazing and particularly fun to watch.