Here are my top 5 favourite.
(Please try to limit it to 5)
1. Aegyo
2.Geu ruh ji (sounds like Guci/kitchi) - meaning Right?
3. Kwaenchannha (probably the most used word in Korean lol)
4. Waaah!: I know this is an exclamation, not a word, but I LOVE how they say it.
5.Jinjja