On grammatical class:

bu'a'a
naturalistic interjection: used to express a fit of overwhelming or uncontrollable laughter; the stereotypical 'evil laugh'
e'e'e
naturalistic interjection: shy giggle
xa'a
naturalistic interjection: laughter
xa'a'a
naturalistic interjection: laughter
xai'a
naturalistic interjection: Hyah! (battle cry/kiai)
xu'u'i
naturalistic interjection: a controlled, focused breathing technique (used for coping, as with pain, fear, etc.)
xy'y
naturalistic interjection: in thought/contemplation