Muhahahaha, I vote "hae?" XDDD
because in Germany wie sometimes say "hae?" If we don't understadn what's up, like this uguu stuff here xD
I don't get it XD
But hey... UGUUU~~~
Romanians also use stuff like that. The cooler guys (like me) (AKA guys/gals who watch animes & stuff) use "haeeeee?" or "soooou nee?" but never Uguu~ xD
We do also use "Ai?" (read like in japanese) - used mostly either at the country side or as a joke
And "Ăă?" ( it's a sound close to the one in the disgusted "ugh". (the u part) )
Exclamating "Auuu!!" means that you hurt yourself. Like ouuuuch.
Buuut this is a hole other story! ^^
So i vote for hae !
(Also, this reminds me. Why do all Korean words seem to be mono-syllables?)