Depending on the temperature, I either sleep in nothing or if it's cold out I sleep in cotton pajama pants and a t-shirt. I actually have quite a collection of pajamas though, I wear them to lounge around the house after work!
I get really cold! Right now.. Gray pants with a little Hello Kitty, a short red spaghetti strap night thing with pink hearts and a matching hello kitty shirt over that. Will be switching to light gray hello kitty and pink thing tonight. X-)