What's a 'secondary starter' pokemon for every region?

Like, we can consider Pikachu (and Eevee) in Kanto to be treated as starters by the franchise, and in Johto you technically start with Togepi, so that's the one for Gen 2. Riolu is commonly used and good even late-game, plus it has a mega and is given starter levels of attention, so those for Sinnoh. (Alternatively, Bidoof, because it is iconic) Kalos has... very few original pokemon, but it has to go to Fletchling, one of the best regional birds. The player even has one in their house.

What about others?