its okay thats love, dots, signal, age of youth,
I don't re-watch dramas, I just like to re-watch some scenes that I liked.
But right now I'm rewatching Age of Youth because it's on Netflix.
I don't usually do rewatch, but i've re-watched Goblin, Weightlifting Fairy, Strong Woman and Moon Lovers.

You who came from the stars - I've re-watched this trying to figure out why it got so popular.
MY MOON LOVERS
Cruel Romance
Boss and Me
Cubic
Leh Ratree 2015
The Holy Pearl
Rooftop Prince
Healer
Moon Lovers: Scarlet Heart Ryeo
1. All itazura na kiss versions
2. Healer
3. The moon embracing the sun
Master's Sun
Secret Garden
Moon Embracing The Sun
Autumn's Concerto
Strong Woman Do Bong Soon (but only because my cousins want to watch with me) 
Coffee Prince
You Who Came From The Stars
Scent of a Woman
Marriage Contract
It's Okay That's Love
Marriage Not Dating
Secret
Queen In Hyun's Man
I don't normally re-watch dramas but there are a few I have watched multiple times...

1. Kimi No Te Ga Sasayaite Iru
2. Battle of Changsha 
3. Tatta Hitotsu no Koi
4. Winter Sonata
5. The Final Verdict
Since I am a declared re-watcher I made a list: http://mydramalist.com/list/73DgrkkL just to know what to watch again XD
Rewatched No 1 for 4 times, 2 to 7 for 3 times, 8 to 15 for 2 times, the rest just one rewatch. (until now ;P)
In the list are just the dramas I re-watched in full length, the ones I just watched some episodes ore scenes do not count for me as re-watched.

The same with movies http://mydramalist.com/list/74KoPZV4
Healer, Plase love the uselesss me (jdrama), in time with you (tw drama), another oh hae young, Kill Me Heal Me, romantic doctor teacher kim, ... I always rewatch dramas when I dont have a new one. But I think Healer is the one I rewatched the most (3 or 4 times). Sometimes when I am currently watching I rewatch the episodes so far, I did it with Lucky Romance and strong woman do bong soo (the waiting was killing me). 
Healer
love in the Moonloght
pinocchio
secret
Well for some reason, I started rewatching oh my venus lol, love the OST btw, especially darling u
I never rewatch a drama, I once tried to rewatch my 1st Korean drama, oh my lady which I liked, but it felt too cheesy ...
So it's a big deal for me to be able to rewatch and enjoy a drama, especially when it's not over yet, but I did that recently with Circle, and I loved it even more then the 1st watch!
1. healer
2. signal
3. dots
4.goblin
5.coffee prince