Flan’s Mod is a large mod containing over 50 content packs which each have trucks, tanks, airplanes, mechs, and many more vehicles and weapons. The WW2 pack is the only one that I have played but is also my favorite. It adds tanks, weapons, airplanes and armor from over 7 different countries. The most impressive thing about this content pack is the models of the machines which go way outside of the square Minecraft universe, and the functionality  of all of the machines. Both of these combined can let you reenact famous battles with your friends, or finally teach those creepers with a tank shell to the face.