Haven't watched it but i would choose the lead actor, Chun Jung Myung.

She was pretty 
this is the first time I experience second lead syndrome. . . I choose Kim Shin Hyeok - (Choi Shi Won )

The Imperial Doctress
N/A (I haven't watched it.)

Mary stayed out all night
Jung In (Kim Jae Wook)

Reply 1988
N/A (I Haven't Watched It)

Hwarang
park seo joon
trot lovers
N/A (I Haven't Watched It)

Beautiful Gong Shim
Nam Goong Min

Sassy Go Go
Lee Won Geun

The Best Hit
Haven't watched it yet but I like Yoon Shi Yoon :D

She Was Pretty
Park Bo Gum

Ruler: Master of the Mask
yo seung ho
reply 1994
N/A

You're Beautiful

Probably Hwang Tae Kyung (Jang Geun Suk) but more based on his look than his behaviour^^

Reply 1988