Morning Musume: Sayumi. She is gorgeous, and cute, silly, and a really hard worker who doesn't give up, even after she fails. She just gets better next time! I love that.

Next would be Takahashi Ai because her vocal talent just BLOWS ME AWAY. I also love how she can dance, sing, and do really great facials all at once! It's such a good performance!
Berryz Koubou- Miyabi. She is so pretty, and has a really nice voice. She always sounds great live, and has really good control over her voice, I think. She knows her range and everything, and hits it all well. Plus, she was the first Hello!Project girl who stood out to me. I first found Buono, and she had the lighter hair and I thought she was pretty, and learned all her parts for the dances. She just sorta grew on me.
C-ute- Airi. My favorite idol.

She is perfection. Gorgeous, yet still little-girly cute. Confident and a fantastic performer. She can really dance, and has a voice that just ALWAYS sounds good. She has one of the (top 3?) best voices in the Hello!Project, in my opinion. Then, to just add to it, her personality is adorable. She is silly, and funny, and so goofy. She can be immature, but in a cute way. She is just herself, even when it earns her some strange looks.

I adore her.
S/mileage- I don't know this group to well yet, but from what I see, I really like Yuuka. She can dance well, and is the cutest of them, I think. I also saw her in High King and thought she was great, so I think it'd be her.
Hello Pro Egg (Does this count?)- Saho Akari. This girl has serious talent and needs to debut in something, like, now. She can sing, and she rocks dancing. She has a very unique looks to her, that I somehow really think is strange yet adorable. Hahaha. She rocked in Shugo Chara Egg, but she really stood out to me in Aa! She was with my two favorite in the Hello!Project, and she was just an egg, but she really did fantastic. You never thought something like: "Well, she is just an egg, so it's ok." because she kept up with them perfectly!
Does Buono count as an active group? Obviously my favorite is Airi, but yeah. I love this group, so I really hope they continue.