Personally, mine is joint first between Sandshrew (the cutest), Espurr (most relatable), and Gastrodon.
After those, in no particular order, I like Turtwig (best starter, fight me), the Roggenrola line (little rock guys), the Litwick line (candles and lamps with nefarious intentions), and Metagross (cool robot thing).
Kyogre is the best legendary in my opinion
It took soooo long, too! The line was aching for a third evolution since the first gen, but at least when it came it was an S tier. Scizor is for sure in my top five, been a favorite since it first showed up. Technician Scizor with bullet punch fucking cleans up and looks cool doing it.