Guys do you know there's a nice neutral word "член" in Russian?
I recommend using it instead when you don't want to sound rude as you do when you say "хуй".
Btw can you range the synonyms for pennis by rudeness, please?

Here's the one in Russian (rudeness accending):

Прибор - Somewhat respectful meaning, as of the thing of a good size
Достоинство - same as previous
Аппарат - same as previous
Фаллос - neutral, bookish
Пенис - neutral, a tiny bit bookish
Член - neutral, can be used either formally or in informal speech (short for (мужской) половой член)
Хрен - colloquial
Писька - widespread between kids under 12 y.o., they tend to call it so when speaking with each other. Can as well refer to the vagina. Universal. That's why it's used amongst kids.
Писюн - widespread referring small penices of boys by their parents, since it's masculine, it sounds kinda respectful compared to писька.
Пиписька - same as писька but slightly derogatory as if it is small-sized. Refers to the pennis only. Childish.
Стручок - small-sized, derogatory
Елда - rude, large sized.
Хуй - rude. Used in cussing a lot.

Of course if you say писька, писюн, пиписька referring to the pennis of a man, it will sound derogatory as if it were as small as the one of a boy.