Song Joong Ki if you watch Descendants of the Sun !!!!!!! Please watch it if you haven't I swear its a love at first sight drama ????
basically the cute guy in my avatar SONG JOONG KI!
Yoo Ah In & Kim Ji Won <3
i've had a major crush on ji chang wook and song joongki for the longest time,
but if we're just talking fave actors then definitely sung dongil and ahn naesang
So Ji Sub, Lee Sang Yoon, Song Seung Hyun, Mike Pirath and Ji Sung! <3
So Ji Sub is at the top of my list right now. <3 Major kdrama crush (but not a fan of his wild hair in some of his older stuff!)

I also really like Seo In Guk and recently discovered Ryu Soo Young

Sometimes it's more of a character I'm into than the actor. I find I really like them in one show, but not so much in another.
Winner: Hyun Bin 
Runners-up:
1. Kim Soo Hyun
2. Song Joong Ki
3. Jo Jung Suk
I love Yoo Seung Ho, Song Joong Ki, Jin Goo, Yeo Jin Goo and So Ji Sub. Also, lately new actor Kim Min Jae is stealing my heart.
There are so many I like. But I'll just give my top two female/male because of the quality of their acting and how it impresses me.
Gong Hyo Jin and Ji Sung.
Song Ji Hyo, Yoo Seung Ho, Nam Goong Min, Choi Sooyoung, Bae Jong Ok
Jang keun suk 
Ji Sung
Rain
Seo in guk 
Lee Jong Suk... I have watched everything he is end (including High Kick.. talk dedication) and for me he just shines in everything he is in. The first show that made me fall in love with him was I Can Hear Your Voice, which remains one of my favorite dramas I've ever seen. Also, he chooses dramas very well, if you look at the stuff he has been in from the last few years his dramas are always very successful and high rated.  


Ji Chang Wook - his acting in Empress Ki got me hooked
Song Joong Ki
Yoo Ah In - honestly, when I first saw him in Six Flying Dragons, I thought he looked rather fugly
Been A fan of Gong Hyo Jin since watching It's Okay That's Love..
And Joen Do Yeon steal my heart lately in The Good Wife. They're both awesome and cool