Fly a kite. This use to be a many-hours-long activity for kids that has gone by the wayside to video games. Consider taking a trip to your local toy store and picking out a fun kite. Do any of you remember the ones that looked like bats that had eyes on them? Those were my personal favorite. Spend the day at the local park teaching him how to fly a kite. This is a great opportunity to talk about the weather, literally.
Visit a Barber Shop together. I mean a good old fashion barber shop, not the up-to-date salon with a chair station. Make a day out of it and hit an old diner or soda shop and then head over to sit in the big chair and get haircuts. This is a great way to just hang out, guy-to-guy, and spend a day together.
Build a rocket or an active volcano. Yes, I know, those days spent finishing a class project can fill your mind with terror of taking on another "typical" art project, but this time, make it for fun, not a grade.
Work on a car together. This use to be a right of passage for fathers to teach their sons how to work on a car before they could ever get behind the wheel, but sadly, a lot of men really have either no time or no idea how to work on their car. Start with the basics, change your oil, change a tire, check the air pressure in the tire. No idea how to do any of that? Make it a project to learn together. This not only teaches them about the basics of how a car works, but also gives them the satisfaction of a job well done.