Day 12: Brock
Sometimes when looking for good first bosses, you need to take a look at the very first boss of a game series. With that said, Gym Leader Brock.
For many Pokémon fans, Brock was the very first gym leader they've ever faced, and he really set the tone for future gym leaders not only in the original Red and Blue, but for all gym leaders in the generations that came after this one.
Brock here specializes in Rock-type Pokémon, and I feel that that's a very fair type that a first gym leader should have as it, along with the Ground-type, has some relation to the starting types of Pokémon. If you started out with the water starter Squirtle or the grass starter Bulbasaur, you're most likely going to have an easy time against him, but you're in for one hell of a battle if you chose the fire starter Charmander or if you're playing Pokémon Yellow where you have a Pikachu as your starter...or, you know, Mankey exists.
Brock's team only consists of two Pokémon: A Geodude and an Onix. The Geodude is undoubtedly his easiest Pokémon as he doesn't have any rock type moves and his only attacking move is Tackle. Depending on which version/remake of Generation 1 you're playing he'll also have Defense Curl to boost his physical defense, making it harder to take down.
And then we get to Brock's Onix. In the original Red/Blue/Yellow, like Geodude, Onix doesn't have any Rock-type moves, but he's still a decent wall for this point in the game. Yellow tried to make Onix more challenging by giving it the move Bind to slowly whittle away at your health, but still not too bad. But starting with Fire Red/Leaf Green, Onix has a Rock type move that makes it a force to be reckoned with and a nightmare for anyone starting with Charmander (Unless you had the hindsight to catch a Mankey).
In Fire Red/Leaf Green, Onix comes packing with Rock Tomb, a strong Rock type move for this point in the game that can even lower your speed, and in the Let's Go games he has Rock Throw which, while not as powerful as Rock Tomb, still takes advantage of the same-type attack bonus, and he replaced his Tackle attack with the strong Headbutt move that has a chance of flinching.
Like I said, having a water, grass, or fighting move is great for this fight, but it can be a doozy if you're not prepared.
Now some of you might be wondering why I chose Brock instead of Roxanne or Roark, two other first gym leaders that specialize in the Rock-type, especially since they seem to use Rock-types more effectively. I mean, not only do their own Geodudes have threatening Rock Type attacks, but Roxanne takes advantage of the defensive nature of Rock-types with her Nosepass, and Roark not only has that Cranidos with moves that hit like a truck but he also has the then new move Stealth Rock, making it so if you switch out then the Pokémon you switch out to takes damage. Why don't they make the cut but Brock does?
Well, as I mentioned before, Brock was the first gym leader most Pokémon fans have ever faced, so there's a lot of nostalgia involved here. He also set the precedent for gym leaders to follow. Also, I view Roxanne and Roark as gym leaders who built upon the battle with Brock. Without Brock, the fights against Roxanne and Roark probably wouldn't be as good or even challenging.
I'm picking Brock not only because of his fun fight that tests your knowledge of typing, but also for being a nostalgic fight that sets a good example of what future fights in the series will be like.
What else can I say except that Brock absolutely rocks.