Normally I'm not a fan of rewatching a drama, but there are some special cases.
1 Litre Of Tears - Watched it 3 times. It may sound weird, but whenever I watch it it helps me to keep going.
White Christmas - Watched it 2 times. I wanted to see if the killer did anything suspicious in the beginning, so I rewatched it.
Shut Up Flower Boy Band - Watched it 2 times, because I love the soundtrack.
Liar Game 2 - I'm currently rewatching it the second time, because I forgot what happened and I want to refresh my memory before I watch the movie.
Hammer Session - It was one of my first dramas. The first time I watched it in the internet, I really liked it so I ordered the DVD and watched it again 2 times. Once on my old TV and once on my new TV in HD.