KaM and K'nex?
Being a KaM player back then, I made some buildings and units from KaM.
StoreHouse
Inn
Quarry
Weapon's Workshop
Iron Mine
Metallurgy Shop
WatchTower
Units
Latter on, I made more realistic looking horses.
If you are into K'nex (I'm not sure how well-known K'nex is outside of the U.S.A.), you can use this gray connector instead to make the knight's horse.
Lastly, I did make a few siege weapons from Age of Empires 2 the Conqueror's Expansion, but here is the "onager" which can be the catapult in TPR.
(I made the Trebuchet from AoE2 which you could pack and unpack. It could take a 2 pound (about 1 kilogram) counterweight easily, but it did fire a decent sized projectile 35 feet (about 10.5 meters) with a 5 pound (about 2.25 kilogram) counterweight. If anyone is also an AoE2 fan and/or K'nex fan and is interested in seeing the plans (in picture form, let me know).
What makes me an Expert isn't my skill in of itself but my desire to win big.