I think all the new Rotom Forms are stupid and unnecessary, so I like its original form the best.
It was cool when Eevee could evolve into a bunch of different forms. Deoxys forms were a pretty cool, new thing too, but those were supposed to be unique. Now you've got Gardenoir/Gallade, Glalie/Froslass, Rotom, Shaymin, Giratina, and Arceus who all have different forms. It's just taking away the fun and origanality of Eevee and Deoxys and making the whole "forms" thing kind of annoying. Plus, all the new Rotom forms are just plain stupid. Lawn Mower? Toaster? I mean, common, people.