Eevee is so cute, and awesome, a bunny/dog, what’s not to love. If I could only pick one, Eevee would win. The Manga version that was experimented on and can become all three of the original transformations at will is really awesome, despite the terrible reason behind the power.
Charizard is a cool and badass dragon (I know it doesn’t have that typing, but come on).
Gengar is cool and slightly creepy, but ultimately a fun-loving troll.
Mewtwo, one of the most iconic and cool Pokemon, love his design, backstory, and powers.
Pikachu, basic, but there’s a reason that it’s one of the greatest icons in the world. Cute and fun.
Greninja is a great newer design, also fun to play in Smash (even if not the most competitive).
There are a lot more, but I’ll stop there.