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
Nidoqueen but only because the in-game trade in the original games is named TERRY.
When I battled a friend a few years ago after using her we laughed for awhile about the name. It became a meme between friends, and for that reason she’s my favorite.