Overboard! by Sarah Weeks, illustrated by Sam Williams. 

Doing a toddler story time?  Do I have a book for you!  Overboard is the story of a little baby bunny who enjoys throwing all sorts of things out of his high chair, his crib, the bathtub, etc.  The book has charming pictures that share the joy of throwing things down.  The illustrations are combined with a bouncy, rhythmic text that will engage toddlers and preschoolers immediately.  This one is perfect for sharing with groups but will also be enjoyed one-on-one.