Someone gave our little man a dinosaur egg for Christmas. The egg is part of a "growing pet" family of toys which you can put in water and over a few days develop from egg into a normal plastic toy.
The actual toy is not that great (feels like a cheap rubbery model of a dinosaur with poor features and colouring). However the process of "hatching" and checking up on progress was great. It kept our son entertained for days with huge excitement building as the egg shell cracked and the head of the dinosaur appeared. So it's a fantastic tool for building patience in your little ones :-) You can get these eggs (for all sorts of animals) for about $5 in most toy stores or online.