Coat of arms activity- I failed to give an example of how exactly I wanted it done so several of them took it as a writing assignment and just wrote words.
Shishkabob Catapult- The premise was nice. The construction was not strong enough to actually apply any physics to hitting premade targets. So when in doubt- just throw the ammo (marshmallows) One kid invented the cross bow with his and it was plenty effective. Then he held it up and said "Look, it looks like a cross." And I said "hence the name...." A light bulb went on.
Using runes to code the notes for class and having them decode them. One student said "it made my brain tired but I liked it."