There are actually many...actually i mostly like all SHINee,Apink,and Snsd's songs...but i will just recommend here some of there songs:
Luv(Apink)
Lucifer(SHINee)
Genie(Snsd)
(maybe i will just write their non-title songs hehe..cause title songs are easy to found in youtube or more popular than the non-title songs)
In my Room-SHINee
Real-SHINee
Four Seasons-SHINee
Chocolate-SHINee
Hold you-SHINee
Trigger-SHINee
Love Sick-SHINee
The Reason-SHINee
Selene 6.23-SHINee
I'm with you-SHINee
Life-SHINee
Quasimodo-SHINee
(there are really many songs of them..but i just list a little)
I Do-Apink
Perfume-Apink
Fairytale Love-Apink
So Long-Apink
What a boy wants-Apink
Dejavu-Apink
Secret-Apink
Like a dream-Apink
Secret Garden-Apink(im not sure if this is a title song or not cause it has a mv and a title of an album..)
The wave-Apink(this is only their 5th anniversary song for fans but it has a mv)
April19th-Apink
(there are many songs of them too)
Mistake-Snsd
Baby baby-Snsd
My Bestfriend-Snsd
(i cant write anymore)

GRAY - 하기나 해 (ft. loco)

I live for song recs. Here's a bunch.

느낌적인 느낌 - Champagne feat. Minah
Fall In You - As One feat. Candle
보란듯이 - Sonnet Son, Andup
나도 알아 (I Know) - Candle, Hanhae
Love Letter - Sanchez, Microdot
Could You Be Mine? - Phantom
다시보기 - Kiggen feat. 진실, 한해
스르륵 (Smooth) - Aoora feat. 세리
To Violet - Rex.D
양아치 - Imfact
Shine - Imfact
Ticket - Cheeze
Sing Me - Day6
Emotion - Mamamoo
Stop Running From Love - G.Soul
Like You - Hoody
Into You - Eric Nam, Kolaj
오버액션 (Over Action) - Hanhae
올해의 남자 - Hanhae feat. D.meanor
Side Mirror Girl - Louie feat. Sanchez
Midnight Sun - Hotshot
Driving - A.cian
That's Why - Baek Yerin
Say Yes - Niihwa
#불편해 - Rex.D feat. Kang Minhee
Betting Everything (acoustic ver.) - Royal Pirates
Let U Go - Royal Pirates
Over You - Pae Su Jung
Back - iOne
초록창가 - AKMU
시간과 낙엽 - AKMU
괜찮아 - Andup feat. 샛별
기시감 - Andup feat. 달총
여전해 - Andup
Knock Knock - N.Flying
1분 (1 Minute) - N.Flying
By My Side - Ian Kim
First Love - Jung Heechul (ZE:A)
Collection - Kevin (ZE:A)
바디 로션 - J'Kyun feat. JYO
첫차 타고가 (Stay Up All Night) - J.Heart
그대와 같아 (Same As You) - Jooyoung
ICU - Choix2 feat. Andup
밤에 본 한강 - Pro C feat. Eunha
너만 봐 - UJi feat. The Channels

Oh how could I forget though: GB9 - Going Crazy

Outsider - Acquaintance
Kream - Dalla
Epik High - Over
Epik High - Nocturne
Epik High - Scapegoat
912 - Approach
E.via - Diary
Puer Kim - Manyo Maash
ChAOS - Kiss Kiss
John Park - Falling
Standing Egg - Miss You
Standing Egg - Confession
Brown Eyes - Don't Go Don't Go
Mot - Cloudy Seoul
eAeon - Drug
eAeon - My Anniversary
eAeon ft Lena - You Don't Know Me
Urban Zakapa - All the Same
Clazziquai Project - Romeo and Juliet
Ft.Island - Memory
Broken Valentine - Aluminium
Jace - Goodbye my Ray
M.I.B - Bounce
M.I.B - Nod Along
Lucia Woohyun duet - Cactus
I have way more but it would take forever to list it all down. If you want more though, feel free to PM me.