Phun calls it self "a 2D physics sandbox" program for making grates physics on a interactive whiteboard or a tablet works good also.
From Umea University in Sweden this brilliant piece of free software for none commercial use comes. Create a car that rolls down a hill or paint whatever you like - this is pure "PHUN"
Remember to set the alarm clock since you will be lost in time when starting using this program!

You can download your copy directly from Phunland.com

We give this one top grade:
 

Check out this YouTube video from the creator himself Emil Ernerfeldt.