from the newer gens, I enjoy a lot of the paradox pokemon. Iron hands and Roaring Moon are my favorite design wise, but Raging Bolt is def my favorite when actually playing the game.
I usually change my favorite Pokémon after some time. For now my favorite Pokémon is Venosaur. First because I like the esthetics but also because it was the last Pokémon I had against the champion, in my FireRed Nuzlock , and it won the game by hitting all the sleep powder. Either way I will probably change my favorite Pokémon by the end of the next Nuzlock still it will stay at the high of my tear list for the rest of my life.
Snorlax for sure just because the ridiculously fun name. But that's probably because I'm Swedish, it basically means snot-salmon if translated which is even more ridiculous