I'm thinking that it would be Tony the Tiger. Frosted Flakes have always struck me as being a good cereal (plenty of sugar, not too many nutrients to divert the taste buds) and, well, I've always been more partial to non-human mascots and bold pronouncements.
They're GRRRRRRRRRRRRRRRRRREAT!
Ahh, I apparently stole ShellyMC's idea. C'est la vie!
but i always kind of liked Tony the tiger because he was so
energetic..
"Theiirrrr Greeaattt!!"