Not exactly a boon to productivity

Are you looking for a way to goof off during the day, but your employer's Internet filters won't let you surf YouTube? Why not slack off in a more hands-on fashion? Check out Mini Weapons of Mass Destruction: build implements of spitball warfare by John Austin. Whether you're a budding engineer, an inverterate tinkerer, a 10-year old boy or someone who hates to throw anything out, this book will suck up hours of your time.
Start out easy, with a bow-and-arrow made from a bendable plastic ruler, a rubber band and the cartridge of a ball-point pen. Work your way up to a crossbow of #2 pencils and rubber bands, and finish up with a paper-clip trebuchet. Make darts from the ends of old shoelaces, use deflated balloons and toilet-paper tubes to make a coin shooter, or a water bomb using a simple piece of paper.
The fact that the book starts with a long list of safety precautions (ear protection for making the minibombs, and eyeware protection for everything) will clue you in that this is not a book you hand to your 9-year old and walk away. This is an excellent introduction to physics and engineering with adult supervision, and what a totally cool way to bond with a kid that can't seem to let go of the DS (if you don't know what a DS is, consider yourself lucky to have dodged that parental bullet).
This is also a great gift idea for Father's Day.