Over the years .... when I had an extensive pokemon card collection, I don't think I could answer that question correctly, because I had at least a dozen favorite cards, in multiple languages (Japanese, French, German, even a dual language card), none of which I could possibly rate more favorite than another. Once we started selling sets and downsizing after my retirement from the trading card game, we only kept a bare minimum - mostly for nostalgic reasons. So I guess now the only favorite pokemon card I currently own would be a first edition shadowless Charizard.
What's your favorite pokemon accessory? In this case I'm sure people have trinkets, toys, figurines, games, plushie, books, electronics, clothes, hats, etc that have pokemon art on them or are shaped like a pokemon. What's your favorite (non-card, non cartridge) pokemon accessory? And why?