Non-Legendary Pokemon that cannot breed:
Nidorina, Pichu, Cleffa, Igglybuff, Togepi, Elekid, Magby, Smoochum, Tyrogue, Wynaut, Azurill, Happiny, Mime Jr., Munchlax, Bonsly, Mantyke, Chingling, Budew, Riolu, Nidoqueen, Unown
Legendary Pokemon that cannot breed:
Articuno, Moltres, Zapdos, Mewtwo, Mew, Raikou, Entei, Suicune, Lugia, Ho-oh, Celebi, Regirock, Registeel, Regice, Latias, Latios, Kyogre, Groudon, Rayquaza, Jirachi, Deoxys, Uxie, Mesprit, Azelf, Dialga, Palkia, Heatran, Regigigas, Giratina, Cresselia, Darkrai, Shaymin, Arceus, Victini, Cobalion, Terrakion, Virizion, Tornadus, Thundurus, Reshiram, Zekrom, Landorus, Kyurem, Keldeo, Meloetta, Genesect
"baby" Pokemon will not produce eggs:
Pichu, Cleffa, Igglybuff, Togepi, Tyrogue,Smoochum, Elekid, Magby, Azurill,Wynaut, Budew, Chingling, Bonsly, MimeJr., Happiny,Munchlax, Riolu,Mantyke.
Ditto cannot be bred with another Ditto. Furthermore, genderless Pokemon (e.g., Magnemite) can ONLY bebred with Ditto; anyother pairings will not produce an egg.
Finally,Pokemon can only be bred with other Pokemon in their particular Egg Group. The Egg Groups may be confusing--(why are Wailmer and Wailord in thesame group as Infernape and Blaziken)--and some Pokemon belong in two different groups. Pairings that cross between non-matching Egg Groups will not produce eggs.