Well, I assumed that my first post would be in a thread like this. Mine's Venonat, it did actually become my favourite Pokémon thanks to its evolved form, Venomoth. The first time I saw it in the Safari Zone (in Pokémon Blue, I think), I became really suprised. I'd never heard of a Pokémon like that. Maybe it didn't look that spectacular, but I thought that it looked really extraordinary in some way.
It was my favourite Pokémon for a while, but after a certain amount of time later, I found out that Venomoth was Venonat's evolved form (I was quite young then, I thought that Tauros was Pinsir's evolved form because of the horns and the fact that they're just one number away from each other in the PokéDex). And because of some strange reason, Venonat became my favourite Pokémon instead of Venomoth. He do look very cute and huggable, don't you think so? ^_^