Here’s a glossary of onomatopoeiac sound-effects used in Japanese comics and what they mean. Lots of interesting, nonintuitive definitions here:
Gunya = sudden mental realization
guon = the sound of a dryer. For the sound of a washing machine, see goun
guooo = a roar. Can be a fire sound, often used for Hiei’s fire attacks (Cf. bo, goooo, po)
gura = stagger, move shakily (see also zuru)
guri = to give noogies
(Thanks, Betsy!)