My favorite preschool toy is a 100 piece puzzle.
(Fort Lewis, WA, US)
For my sons 4th birthday he received a 100 piece scooby doo puzzle. I figured he was too young for this so I put it up. I few days later he was asking for it. I had to get some work done around the house and did not really want to hear all the frustration that was about to happen. I got the puzzle down for him and told him to go ahead and try it on his own and in a few minutes I will help him out. I go back to my chores and after about 10 minutes of complete silence I go and check on him. He is sitting at the table completely focused trying every piece in spots to see if it fits. Once he was finished he took it apart and did it again. When I need a few minutes to get something done without being interupted I now give him a 100 piece puzzle.