M.O.
We found a plastic baby doll to be endless entertainment. You can wash her, put lotion on her, dress her, diaper her and walk her around in a stroller. It's GREAT training too if you're ever planning on having another child! It teaches your daughter to "be gentle" to a baby. It will be her best friend.
Plastic ones can get washed off- which is key at this age. Forget anything stuffed!!! (Some have plastic faces but stuffed bodies.)
If you're looking for something even better, they have some that will pee pee on the potty and take a bottle of water/juice (which makes the pee). This was our "next" purchase.
Seriously, ENDLESS entertainment. You can even buy the dolly a whole travel system with baby carrier, stroller, pack n play (and the carrier also can turn into a high chair and swing!).
Also, for a different idea, what about a bug catcher box? Ours is clear plastic and came with a net. Our kids LOVE catching bugs and watching them through the windows. You can also catch frogs or whatever else. If my kids see a butterfly on a flower they go running for the little net - it's too hysterical to watch them chase it.
If your looking for a "big toy" I strongly suggest a sand and water table. Talk about endless entertainment!!!! You can bring it indoors in the cold weather and fill it with dry rice. Outside sand and water or even water/bubbles are awesome. It's a bit messy outside, but a great way to keep a little one entertained and rather contained at the same time! Our preschool keeps these in the classroom and regularly fills them with different toys that match the theme of the week - like toy cars, balls, colored rice, colored ribbons, etc.