Animal Onomataopoeia

chuu chuu	Squeaking sound as in the sounds of mice, hampsters, kissing, insects, and other such noises.
gara gara	Snake sound.
hiin hiin	Horse sound.
kero kero	Frog sound.
kyonpy	This is not so much a word as it is an action. It is a meaningles word. "Kyon" is a visual action of rabbits jumping and "-py", or "-pi" is a childish sound
mane mane	Monkey sound. Mimicing sound.
nyan nyan	Cat sound. The word, "nyanko" is a childish way to say cat, as in "kitty".
pao pao	Elephant sound.
piyo piyo	Chick or small bird sound. (cheep cheep).
poi / paku	Sound from a carp's mouth. (koi = carp)
wan wan	This is the 'sound' a dog makes.

People Onomataopoeia

butsu butsu	Whispering sound.
dosun dosun	Walking sound.
gaku gaku	Trembling sound.
gaya gaya	Crowded area.
gyaa gyaa	Screaming sound.
hotto	It is the sounds of being relieved.
kyaa	Scream.
pachi pachi	Clapping sound.
pero pero	Sound made from licking candy.
tamaya	A word used to cheer for good fireworks.

Inanimate Objects & Misc. Onomataopoeia

ban ban	"Bang bang"
biri biri	The sound of electricity
dokkan	The sound of crashing into something.
dosun	Thud when something hits the ground.
gari gari	This is the 'sound' a drill makes.
gasa gasa	Sound of something that is dry and rough.
jara jara	Sound made from a ball falling from a Pachinko. Pachino is a gambling device similar to a slot machine that uses balls instead of tokens.
jori jori	Sound of rough, unshaven whiskers.
pan pan	Banging sound.
ting	Sound when a ball falls through a hole in a Pachinko.
zaa zaa	Rain sound.
zabbun	The sounds of jumping into water