Smile, You ....Real comedy ...  It is literallly ROFL Out Loud until my stomach hurt, Hilarious kind of FUNNY!  

Probably a weird choice, but as a person who is picky with the humor she likes, I really loved the funny side of Descendants of the Sun! In my opinion, their jokes were done just right! 

And I am also laughing quite a lot in Bring It On, Ghost. :)
Funniest kdramas I've watched:

Merry Mary
Once Upon A Time in Saengchori
Oh My Ghost
Kid Gang
Bad Family
Evasive Inquiry Agency


:)
For sure it is She Was Pretty
Playful Kiss i love to hear the cute little voice of Kim Hyun-joong shouting oh ha ni 
Coffee Prince, Full House
Marriage not dating, The lover, She was pretty
master's sun
high kick
you who came from the stars
Reply 1997

Surplus Princess (I didn't like how it ended but it was funny)
Coffee Prince 
Full House
The Lover and High School King of Savvy
Delightful Girl Chun Hyang
My Girlfriend is a Gumiho
Greatest Love (ABSOLUTELY GOLD)
Master's Sun
Reply 1997
The Lovers (PLEASE DO NOT DRINK WATER WHEN YOU WATCH THIS. PLEASE DO NOT. PLEASE.)
Let's Eat 2
Wang's Family (50 episodes)
You who unexpectedly roll in (this is my favourite 50 episodes drama EVER)

High Kick 3!! This is a sitcom. Very, very funny!
Smile, You and Marriage Not Dating
I have only watch couple, and i think theyr been funny all of them. xD 

But nr 1 must be Oh My Venus.
2. Shopping King Louie. (He is so cute and stupid)
Coffee Prince - I had a good laugh with it.
Only You - during the first part.

RomCom's the best but drama is great.