Most of them have been covered, but also archery. Something about archery. Although it's not really SCA, all of my kids have a homemade rock bows that they bring to events and shoot as well (as safe targets). Maybe something about building your own small scale trebuchet or catapault?

Projectiles. My boys are all about projectiles and boffers with the occasional side trip into Beowulf or courtly graces.