The Minhyun - Ong - Guanlin visual combo had such an impact in Korea. Ong is still my favorite male visual from Produce - he has such a unique look.
As for the girls, I really like different members for different things.
Innocent visual - Chaeyeon, Minju
'Model' type visual - Doyeon, Wonyoung
Elegant - Pinky, Hyewon