Erina Mano, the only current Hello! Project soloist. She's a very talented performer. Her songs are very fun, and they make you really happy.
Because she's the only soloist currently, she, in a sense, stands out among the girls in groups (Morning Musume, Berryz Koubou, C-ute, S/mileage).
Anyway, her music is just really fun, and I'd personally recommend her songs to any fan of j-pop.