Haha, my sister was obsessed with them all! She had Powerpuff Girls sheets, pillows, movies, dolls, etc. etc. etc. My favorite would also be Bubbles [for when I did watch the show], mostly because she is blue [my favorite color], and she's nice, but can be mean.
Bubbles is win! I have a lot of PPG merchandise myself. I have a Blossom, Bubbles & Buttercup plush, the movie (DVD), the series (DVD), Him & Seek (GBA) and even have a nice desktop of them on my comp. XD