Full House wins hands-down.
After watching that, I am now Bi's fan

And I have watched all 3 drama series which he appeared in so far...
Sang-Doo, Let's Go Back to School (Bi's first drama series) is not bad as well, but I have to warn you it gets very very sad at the ending part (I was bawling my eyes out at 4 o'clock in the morning after the last episode lolz). But it has its funny and sweet moments as well

Other nice one include:
Sex is Zero (love the main actress...this movie is somewhat similar to American Pie, so be prepared for some gross scenese

)