This thread could comfortably be re-titled 'What In The Blue Blazes Counts As A Fairy-Type, Gamefreak?'
On that note, Celebi and the Lake Trio all scream Fairy. They're twee, floating little creatures with mystical - seemingly rather than mental - powers. I can kinda accept that the Fairy net is cast wide to incorporate oddities like Granbull and Marill, but the corollary is that some of the choices that were left out are very strange.
As much sympathy as I have for Normal, it's tacked onto a couple of lines that would have been quite alright as mono-types. Heliolisk springs to mind.
Lucario has been mentioned, and I'll also throw in another offender from Gen 4 - Garchomp. Ground-types aren't necessarily literally made from the earth itself (that's more Rock's thing) but I can't for the life of me find a single visual trope Garchomp has in common with other Ground-types. Why this bipedal hammerhead shark that also flies like a jet plane isn't Water or Flying-type is beyond me, though I suspect it's because GF were aiming to create a competitive hit (that's one of the issues I have with the Gen 4 roster more broadly - some of the most high-profile species feel explicitly designed, rather than organic creations).