Can anyone help me think of LOW cost gifts appropriate for infants (mostly around 6 months - 17 months)??

I'm doing scholastic book certificates but would like to have something the kids might actually enjoy on the spot since the certificates are really just a half sheets of paper..

Rubber duckies? Small plushies? I'm worried some parents might not be happy with that since I myself am careful about plastics and toy chemicals, etc...

Thanks!!