Missingno. But that's cheating, so... hm. A lot of options here. My unordered top 10 would be:

1) Delphox, 2) Cinderace, 3) Spheal, 4) Incineroar, 5) Mewoscarada, 6) Pichu (with a ukelele), 7) Tinkaton, 8) Emolga, 8) Snivy, 10) Sandslash.

Basically, small cute mons and anthro mons. Surely this says nothing about me. Honorable mention to a LOT of cool Ghost types (Chandelure, Trevenant, Mismagius, Gholdengo) and some stupid ones I like (Vanillice, Wo-chien, Stunfisk, Dragapult). Also Buzzwole and Pheromosa are rad as hell but I'm not as attached to them.