Question

What pokemon can learn shadow ball as a egg move?

Comments

Shouldn't this be closed as the information can be found on the site?

Answer 1

This has the full list of pokemon that learn it by leveling up and by TM. (there's just too many to list!)
http://pokemondb.net/move/shadow-ball

Comments

This is correct. Since Shadow Ball is a TM, then anyone who can learn the TM can learn by breeding.
There aren't any pokemon that can learn a move by breeding but not learn the TM.

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Some Pokemon (such as evolved and legendary Pokemon) can't hatch from an egg, so they can't have egg moves even if they can learn shadow ball from TM.

Answer 2

All the eeveelutions can

Answer 3

gastly, haunter, gengar
and dusclops and duscnoir

my gengar knows shadow ball

Answer 4

After taking enough steps, the Egg will hatch into a level 5 (Generation II and III) or level 1 (Generation IV onward) first-stage Pokémon of the female species's (or non-Ditto parent's) evolutionary chain.

Prior to Generation VI, if the father knows any moves that are TMs or HMs in that game (and in Crystal, moves that are taught by a Move Tutor) that the baby is also compatible with, it will inherit the move. If a Pokémon species that is gender unknown (such as Magnemite) breeds with Ditto, the resultant baby will inherit any compatible TM or HM moves that the non-Ditto parent knows.

source
A Pokemon can inherit shadow ball only if it existed before gen 6, can hatch from an egg (so no legendaries, and evolved Pokemon can know it only if its basic stage can know it), is either genderless or can have a mother (so no all male families), and can learn shadow ball by TM.

I still think there are too many to list in this answer, so you can look at these other lists.
list of Pokemon that can learn shadow ball
list of Pokemon that can breed and are not all male