A useful online dictionnary, for both translator and reader.
Sometime in a manga you hit some signs that are untranslated and they are most likely sound effects (or stuff like "hmph"...), left untranslated by lazy translators (that's normal).
You just have to recognize the character and type it in the search bar, it then gives great descritpion, with multiple possibilities and even sometimes actual example with manga pages.
Note for translators here :
While JParser do a great job with the sound effects as well, I did hit a sound effect it didn't know. It was ゴク. However the website knew it.
That's just one more ressource to use while translating .