My favourites are Treecko / Grovyle / Sceptile (especially since they fixed Grovyle's colour palette) and Oshawott / Dewott / Samurott (perfect example of evolution being a maturing process for Pokémon, in my opinion).
My least favourites are Torchic / Combusken / Blaziken and Chimchar / Monferno / Infernape. Torchic and Combusken I don't mind so much, but I just think Blaziken looks horrible. Monferno I can just about handle, but I hate the design of Chimchar and Infernape. From a design point of view, they are fantastic, given what they're based on; but I just really hate the way they look.
Favorite is Piplup, despite how annoying it is in the anime I love its move pool having water, steel, and even flying type moves.
Least favorite would be Oshawott, it's not a bad pokemon. I actually like the design, but its move pool is kind of boring. It ended up becoming a water HM hoarder for me.
Favorites: Squirtle and Piplup. Blastoise was a beast back in the day for me (he defeated the E4 on his own using Struggle, for goodness sake), and Empoleon was probably my second favorite starter to use. Torchic and Charmander were also favorites of mine, but I've always been partial to water starters. However, Oshawott has been a little disappointing for me.
Least favorites: Tepig and Chikorita. Tepig is purely for aesthetic purposes; I just loathe his design something fierce. Chikorita was the weakest starter I ever used, and the only one I ever ditched halfway through a game.
tomorrow's just a song away.
Piplup for sure, yeah. Empoleon has eleven resistances and one immunity. Fire and Grass both do normal damage and of the weaknesses, fighting types are easily countered with flying moves and ground types with ice moves. Earthquake can take down electric types. If it's fast enough to hit first and strong enough to one shot the opponent, it's invincible.