In the Tiervan Jail, Central Chamber battle, there are several doors which upon being searched will yield items or enemies as indicated:
During either of the battles on the Eastern Field, the Merchant's poorly hidden treasure chest can be searched. Inside you'll find the Bulletproof Clothes and 250.
Similar to the Jail's Central Chamber, the doors in the Masori, South District battle can be searched. Behind these doors you'll find the following:
Several explosive lanterns can also be thrown, creating a 3x3 damage radius.
Zofia's Fortress has two switches which, when activated, will cause their corresponding mines to explode. Each will explode in a 3x3 square, causing up to 60 damage.
Stalactites will periodically fall onto the map during the Tunnel Hole battle, causing up to 40 damage to any character they hit. They'll fall on the turn indicated in the image to the right, at the start of the enemies' portion of the turn.
In either of the Tunnel Cavern battles, the Arachnid Boots can be acquired, indicated by a dimly flashing area near a cluster of mushrooms in the bottom-center area of the map.
During the first Voronese Sewer fight, every two turns, a torrent of filth will spray forth from the grate near the center of the map, striking the tiles indicated in the image to the right. Any character caught in the blast will be shoved, and incur up to 40 points of damage.
In the game's last battle, the Bone Godemiche can be found near the bottom-center of the map. Search either of the tiles indicated in the image.