How do you even choose a favourite?! I love all of them. Vaporeon is my OG competitive battling friend, tanking everything and dishing out good damage. I used Leafeon on my first ever Pokemon playthrough, so special place for Leafeon too. Jolteon is cool and fast and the first Eeveelution I got in Pokemon GO. Umbreon and Espeon have the best designs and they're both reasonably good in competitive. Sylveon is a special princess and qualifies for the baddest bad boy at the same time. Glaceon and Flareon deserve all the love possible.