Aish is the one I use often????
ommo
aigoo
aish
annyeong
I found myself saying Aigoo and Aish recently lol

Also I've been greeting the old Korean Couple who runs a sandwich shop that I go to on occasion with "Annyeong haseo" haha
jinjha 
gwenchana 
odeseyo
aish
ihaega anga
kajima
헐 "heol" which is a slang word and can translate to "what the hell/oh my god"
잘 먹겠습니다 "jal meokgesseumnida" translated to "thanks for the meal/thank you for dinner" it's just like bon appetit but backwards.
깜짝이야 "kkamjjakiya" basically means "you scared me/you startled me"
I really like that sound that they use to make clear they are listening or confirm their attention or when they use "oh" to do so.
I use "omo" and "aigoo" a lot which can be a bit weird since I live in an area with a decent-sized Korean community.

:)
Pali pali - hurry? faster?

just want to add from japanese
Ikku ikku - faster?

I really love korean language. I've been watching kdramas and I can understand few common words. My goal is to watch kdrama without subtitles but I don't know when it will happen. :D
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Few words from my memory:
Aigoooo (I say this even when I yawn lol), Aishhh, Jincha, Omo, Ottoke, Hyung, Noona, Unni, Ajjumma, Yaaah!, Komawo, Annyong, Bianheyo, Kamsahamnida, Shiro, igo boya/mwoya (I've heard this frequently in return of the superman. Curious kids used to say this frequently) , Nae sarang (especially in benteley's tone), wae, andwae, saranghae,
nomu nomu, palli, gatchi mogcha, jugulle, hajima, pogoshipta, mashinnae, daebak, molla, yennal yennal, kyowoo, yeppuda, oppaaaa (especially in Yo Na's tone) :)

건배 Geonbae!

Cheers? .... this simple word it's really useful

I like Korean gestures too.  Like the one for confrontation, where someone leans in over another person's shoulder and talks frankly to them.  Getting in their face without getting in their face.  At least, that is how I see it.