Believe it or not, I think my favourite aspect of Pokemon is actually the merchandise, even though I don't have much of it.
But where the games and the anime have disappointed me a few times throughout the years, I have never ceased to be amazed by the serious amount of awesome crap that Pokemon puts out on this front; it makes Toei look like amateurs. The plushies are spectacular - even the Pokemon I don't like have fantastic plushies! - and the nendoroids are adorable. The TCG, which I would count as a part of the merchandise, has some fantastic art. You can buy replicas of Pokemon League badges; I actually have a set of Kanto and Johto badges upstairs somewhere. You've even got Pokemon lingerie now!
The official stuff is all excellent quality, too. You get your fair share of truly awful merchandise, mostly from the early years, but most of it is amazing. I love how insanely varied it is; there is almost literally Pokemon everything, and it's great. If only I could afford to buy more of it...