My 12-year old niece, Hallie, asked me for a poncho. Like 2 years ago. She wanted turquiose and grey. I finally made her one and gifted it to her for Christmas. Better late than never, as the knitters like to say. :)
I used the Rosa'sCaponcho pattern (it's free Rav download) and made a few mods. I added some ribbing at the neck and the edge, and changed yarn colors every 4 rows for some stripey goodness. Oh, and I knit until it "looked big enough." I used Loops & Threads Charisma yarn. Bulky, soft and cheap. :)
I will have to try to get a couple pics of her wearing it. I didn't have the camera with me on Christmas morning, but she tried it on and it fit perfectly.