My favorite is Snivy, without question. Without him, I'd still be thinking on the elitist mindset that "Gen V can't outdo the previous Generation." Essentially, he served as a gateway to the games as a whole. After having bought several of the action figures, I finally decided upon myself, "I suppose I want to play a video game with him as well."
Although knowing that, I don't know why the reverse wasn't true. An action figure is more hands-on.