Here’s one of mine:
Jenga Fortress
Split Jenga pieces equally and sit in a large circle (on the floor or at a big table). Everyone has one piece that is marked. Then everyone builds a fortress to protect their marked piece (the marked piece must be stood up on its small side).
Everyone gets a projectile. We liked using those thick rubber bands that came on broccoli at the grocery store, but you could use Nerf guns, balled up paper, whatever–as long as it’s not too light and not too heavy.
Once everyone is ready, take turns firing at each other’s fortresses, trying to knock down their marked pieces. Nobody can touch their fortress at this point.
Last marked piece standing is the winner.
My brother and I used to take ordinary household items and make an airplane out of them, competing who can go further (each would get 3 attempts, and the farthest flight is marked).
We started with gliders, but very quickly moved up to powered flights (rubber bands and improvised propellers). We had to stop with the powered flights because it got so far that we lost them.