Pokemon plush are probably the most diverse of any type of Pokemon merchandise just because there are so many different manufacturers and styles. Some particularly popular styles include PokeDolls (chibi-style, similar to the ones introduced in Pokemon Gold and Silver Versions), Canvas (plush that are supposed to resemble a canvas painting due to their pastel colors), and 1/1 (made to be the actual size of that Pokemon!).
My plushies are easily my most favorite part of my entire collection! I love to keep them on my bed (as many as my small bed will permit anyway) and cuddle them. This probably isn't the best practice for a collector but I've always believed that plushies were meant to be cuddled and loved. : p Cyndaquil, as a starter, gets plenty of plush made after him, but as far as I know, Haunter only has one official plush, sadly. I dream of one day having my own house and putting up a huge hammock in a room and keeping all my plush on it. ^_^