arceus, or slowpoke, who is quite rare.
arceus
The rarest Pokemon is Dialga
The starter Pokemon or spritomb
Arceus Shaymin
You can find the bestest,rarest, Pokemon is to go to www.marriland.com/pokemon
Darkrai.
On Diamond and pearl you don't really see many fire Pokemon or electric types. But really the rarest ones are legendarys. Also Garydos is a good Pokemon hard to get without super rod
A red diamond is probably the rarest colour for a natural diamond. Flawless diamonds are the rarest in clarity, and large diamonds weighing in excess of 20 carats are rare.
The names of the Legendaries in Pokemon Diamond are Uxie, Mesprit, Azelf, Dialga, Palkia, Heatran, Regigigas, Giratina, Cresselia, Phione, Manaphy, Darkrai, Shaymin and the rarest of all Legends in Diamond; Arceus.
there is no rarest Pokemon you have to train and train and including shinies there is no real rarest Pokemon at all.
mew2 is the rarest
The rarest Pokemon in Pokemon Diamond are the Pokemon you can not get in Pokemon Diamond, such as the Kanto, Johto, and Hoenn starter Pokemon (Bulbasaur, Cyndaquil, Mudkip, etc.), legionaries [Lugia, Ho-oh (Event Pokemon such as Deoxys aren't really rare), etc.], etc. Pokemon that are migrated from Pokemon GBA games are also rare Pokemon in Pokemon Diamond. Hope this helped! -Pyrenix three words mewtwo and mew The true hardest Pokemon to catch are: Deoxys, Mew, Celebi, Jirachi, darkrai, shaymin, Ho-oh and lugia that is because they are event Pokemon and the events are over, so to get them you need cheats, or trade them with someone who has, and they may not give them up easily.
Arceus and Deoxys are the rarest Pokemon to date