Secret Dragoon Lance spear
After completing the main story quest in the Forest area (Chapter 6_3) and are traveling towards the castle, you can find the hidden Dragoon Lance spear inside a chest in a secret cave next to a waterfall and Lunar Tear, at the following location. Its stats at Level 1 are 250-260 attack and Lt 3 Hv 2 combo.
Secret Engine Blade from Final Fantasy 15
The Engine Blade from Final Fantasy XV can be found in the Factory during the “Twisted Religion” mission, near the end of the main story. After entering the Factory with Pascal, fight through a large portion of the underground factory. Follow the straight forward path until you reach a conveyor belt with hydraulic presses. Proceed through it and run up the first set of stairs. You will then see a small platform (before the second set of stairs) where you can jump onto the tops of the same hydraulic presses. Jump all the way to the left to find the Engine Blade in a chest. The Engine Blade stats at Level 1 are 160-200 attack and Lt 5 Hv 3 combo.
Secret Phoenix Dagger sword
Travel to “City Ruins: Near The Tower”, and turn right just before you cross the bridge, at the following location. There is a narrow way down the rocks to an elevator that takes you to the bottom. You will encounter lots of enemies at the bottom, but none of them are too difficult and you can just run past them. Once the elevator reaches the bottom, proceed left until you reach the water to find a couple of chests on the right side. One of them contains the hidden Phoenix Dagger small sword. Its stats at Level 1 are 130-190 attack and Lt 4 Hv 2 combo.
Secret Virtuous Dignity samurai spear
Not far from the Resistance Camp in the Amusement Park area (Chapter 4_1) is a ladder that goes down into the sewer. Proceed straight forward from the following location to find the sewer entrance. After sliding down the ladder into the sewer, process forward and turn right. Continue forward and take the second left. Proceed forward and climb up the first ladder on the right to find the hidden Virtuous Dignity samurai spear at the top in a small cave. Its stats at Level 1 are 220-240 attack and Lt 3 Hv 2 combo.