Dd is sixteen months old also. Our favourite toys:
duplo (I dont think you can have enough duplo, especially with a girl at this stage, as gender ideas are already forming)
dolls/soft toys and imaginative play items, plastic cutlery, paper plates, pretend foods, bowls, cups etc. A big blanket to put them on for picnics. Sometimes we use real food, carrots etc, to feed the babies.
some wonderful farm/zoo animals, from LearningExpress, a bit more expensive - from $3 to $5 each but worth every penny. I've seen them in a few small shops too. We go into the shop and choose a new one every so often. She then plays with it non stop for several days and it renews interest for the set. Tons of scope for imaginative play, for years. My friend's six and seven year olds get them out when they come over.
books, books and more books. And library books, as many as we're allowed to check out
crayons and paper
stickers for sticking on the paper with the crayons etc
playdough (home made) with the imaginative play items above
some wonderful wooden dominoes with animal pictures on - very cheap from Target, along with the wooden bricks, but lots of opportunity for games sorting them out
music CDs for dancing to (we love Music Together)
sets of letters, we found some great wooden ones in a small toy shop and love putting them in dishes and sharing them out
a big tin of old buttons and beads (watch the mouth though)
bath toys that come out of the bath, we try to be creative and switch things around.
I keep different categories of toys in plastic boxes. I switch the boxes around every so often , so that things seem exciting when they come back out.
If I think of anythign else I'll post again.