Ratatta's official pronunciation is exactly what I always use. There are pronunciations I protest (Poochyena and Arceus, most notably), but not Ratatta.
What's wrong with Poochyena and Arceus? How are they "meant" to be pronounced? (For the record, I pronounce them poo-chee-ee-nah and arr-see-us, respectively).
Both of which are perfectly acceptable pronunciations IMHO, and neither of which is used by the Pokedex 3D Pro, which calls them "Poo-chee-enn-uh" (as in, the "E" is short, nothing like the word "hyena") and "ar-kee-uss" (C-E is almost never pronounced as a K in English and that doesn't match the Japanese pronunciation, so I have no idea what they were thinking. Maybe trying to avoid the pronunciation of "arse"?)
Creator of Jay's Journey (see quote!) "It's not ten years old! Therefore, it sucks!" - Nostalgia whores everywhere