Boys like to do things, and destroy things, and catch things.

If you're not opposed to guns on political or moral grounds, take him to Wade's Eastside Guns and rent a gun for target shooting on their indoor range. http://www.wadesguns.com/

Rent a mountain bike for him and let him hit the trails in Discovery Park. St. Edward State Park in Kenmore has some pretty sick trails too. http://www.parks.wa.gov/parks/?selectedpark=Saint%20Edward

Put him on the ferry to Bremerton and have him check out the retired warship USS Turner Joy, you can climb all around up and down the ladders, on the guns, down into the belly of the ship. Very cool http://www.ussturnerjoy.org/

Take him to the Museum of Flight, they have the Concorde and a retired Air Force One, you can go into the planes and look around http://www.museumofflight.org/

Take him to an Everett Silver Tips hockey game, you can ride the train up from Seattle and the hockey arena is practically across the street from the train station http://www.everettsilvertips.com/schedule/year/2011/39

Take him on one of the Boeing Factory Tours so he can see actual airplanes being built http://www.boeing.com/companyoffices/aboutus/tours/index.html

Take him whale watching, http://www.clippervacations.com/whalewatching

Take him fishing, Trout is open on Lake Washington right now, you can find a nearby store that sells fishing licenses here http://wdfw.wa.gov/licensing/vendors/

Hope this helps!

Take him to a concert at one of our small local venues. Something he likes, or something loud and awesome.

Dim Sum in the ID and a visit to the Seattle Pinball Museum.
For $7 you can play all the pinball you can stand, with lots of retro machines + a few newer ones. You get a wrist stamp, so you can come and go all day.

http://www.facebook.com/pages/Seattle-Pinball-Museum/131237786915560

Is he into comics? You could take him out to Fantagraphics.

ride the ducks. I'm not kidding, I took my forever-bored 13 year old brother on them last winter and he's still talking about it. I would also like to second Wade's, if he's 15 or older. Theo's chocolate factory tour is also fun, as well as seeing a show at the Annex theater one night. Good luck!

If he's into EMP, take him to Viretta Park on Lake Washington Blvd and point out the former home of Kurt and Courtney next door. You could do a "death tour" and hit Hendrix in Renton, then Viretta Park, and finish with Bruce and Brandon Lee's graves at Lakeview Cemetery.

If you're willing to take a day, you could do a day trip to Whidbey Island and go to Fort Casey State Park and walk around-- even if he's not into military history, it's pretty cool to climb through the bunkers and look at the ocean. Afterwards, get lunch or an early dinner in Coupeville, then catch the ferry back.