Heres a resource I made last year collecting common sfx that aren't easy to find online. Alot of nsfw sfx in here. Another resource to use when finding japanese sfx is http://thejadednetwork.com/sfx/
ガチャ- (with a) slamming noise (door, telephone receiver); (with a) banging noise; (with a) clash (broken dish); (with a) clank; (with a) bang
バタン-bang; slam; thud; crash
ぱたぱた- pitter-patter (of footsteps)
スッ- quietly; gently; softly
ぱちっ- snapping, represents a sharp, small sound.
ゴソ- with a rustling sound; (rummaging) around
ちゃぷ splish-splash; glug-glug
ヴー- SFX for trying to speak through a gag
ぐぐぐ- When you feel pressure or something. Originally coming from squeaky noise./ Onomatopoeia, mimic word when moving something heavy (pressing teeth together)
ぐい- suddenly and forcefully (e.g. jerk, poke, shove) vigorously
トロ- sticky; syrupy; pulpy
ぴんぴん- lively; energetic; full of life/ vigorously/ penetrating; grating
きゅ- absorption; suction; attraction
クラアアアン- Kuraaaa~n- It’s an onomatopoeia used when a dog whines
ガク-body trembling; teeth clattering; something coming loose
じん- tingling sensation (e.g. in a leg); feeling numb; painful tingle; throbbing
ゴリ- with force; hard; vigorously
きゅうん- choked up (with emotion); heart-wringing; momentary tightening of one's chest caused by powerful feelings (e.g. parting with a loved one)
ピョコ- for something suddenly appearing in an almost cutsey way, something bouncy and cheerful.
ぐぢゅ/ ぐち/ ゼク- crushed wet messy