Something happened to me & Because I'm stupid FROM Boys over flower
Reset & Fly with the wind FROM Whor are you - school 2015
Bobby Kim sang (don't know the song name)  FROM Doctor Strangers 
Alive  FROM Moorim School 
All song FROM Dream High 
Goyeo FROM Warrior Beak dong soo 
Yang Hwa Jin - It's Alright (City Hunter)
By far my favorite OST of any kdrama.
My Favourite Drama OST's are :

Who are you : School 2015
Empress Ki
Secret
The Princess' Man
Kill Me, Heal Me
It's ok, That's Love
Sungkyunkwan Scandal
Six Flying Dragons
Reply 1988
It's Okay That's Love
Cheese in the Trap
Descendants of the Sun
Same here.
"Fox Rain" just makes me feel sad when I listen to it.
My favorite Korean drama OST are:

Moorim School: Vixx- "Alive", "The King"
The Heirs: Lee Hong Ki- "I'm Saying"
Modern Farmer: Lee Hong Ki "Do or Die" 
Auditory Hallucinations - Jang Jae In (Kill Me, Heal Me OST)

Mask - Kyun Woo (Liar Game OST)

And all of the OST's of The Master's Sun, dangggg perfection! XD
All OSTs of It's Okay, That's Love! Even the Cafe Scene Songs are perfectly my style!  ;) 
I think i love you - Fullhouse
Dream High OST
You are beautiful - Promise You, Without Words
You who came from the stars - Lyn - My destiny
You who came from the stars - Hello, Goodbye
Pinnochio - Every single day - Non Fiction
Boys over flowers - Because I'm stupid, Almost Paradise
Heartstrings - Kang Min Hyuk - Star
The Heris - Lee Hong Ki - I'm Saying
Secret garden
1 liter of tears 
Descendants of the sun
The master's sun
The journey of flower 
It's okay it's love
Touch Love (Master's Sun)
I Think I (Full House)
I'm Coming To You (Queen Inhyun's Man)
너에게 퐁당 (Splash Splash Love)
As Life Goes On (High School King of Savvy)
Someday & Maybe (Dream High)
Losing My Mind (My Girlfriend is A Gumiho)
Perhaps Love (Goong)
Atlantic Princess (Monstar)
You (Healer)
That Man (Secret Garden)
Growing Pains 2 (The Heirs)
without words from you're beautiful
Everything from it's okay it's love
The Master's Sun - so far I haven't heard anything that bests it.