There are so many, but my absolute favourites are Hyun Bin (he's amazing in anything he does, drama, comedy...), Gong Yoo (he's so fresh and natural... I think his talent is a little wasted, but that might be up to his own choices or his agent's), Kang Dong Won (he's ambitious but humble, he's worked with some of the best contemporary Korean actors such as Song Kang Ho or Ha Jung Woo; always makes risky choices and I love that) and Lee Joon Gi (I really respect him; he's a hard worker and also chooses his roles wisely; and he can be really funny in comedic roles such as the one he played in Iljimae).
These are good actors and good-looking guys to me. There are of course other amazing actors who are not popular for their looks. And it also depends on the work, the character and so on.
I also pay lots of attention to actors in supporting roles. Sometimes they steal the scene.
