I know Sylveon is my pfp, but Espeon is my actual favorite. I started with the originals, so initially Eevee was something you only got one of if you didn’t trade. That made it special, and of course it was cute as a button, so I always tried to get one regardless of the game. Needless to say, I was super excited to find out you could catch wild Eevee in Gold/Silver. So I caught one and was determined to try to raise its friendship to get one of the new evolutions. It just so happened to happen during the day, so I got Espeon. The friendship mechanic made an already special pokemon that much better. It helps that it has a great design and a cool type, too!
I’ll go with my favorite team, because there’s no way I could ever just pick one.
Blaziken, who journeyed with me from ruby to pearl to white(shortly, i didn’t actually play this one), to XY, they’ll always have a place in my heart.
Then, Aron, Plusle and Minun, Sylveon, and Talonflame!
Honorable mentions to Mimikyu and Shuppet.