Is chimecho a rare pokemon

Yes, in all generation it is rare.

- As an uncommon Pokemon at Mt. Coronet (40% or 10%) or Sendoff Spring (10%) which you can go to after you defeat the Elite Four. (Pokemon Diamond/Pearl)

- Top if Mt. Pyre. (Ruby/Saphire/Emerald)

~ T.A.P.M. or SM.

Total Caught: 487/487 + Shiny Complete.