Cannon Troopers are enemies that can still be found within the code of The Legend of Zelda: A Link to the Past but were not used in the final game for unknown reasons. The enemy will work perfectly if inserted into the game, although unlike other enemy soldiers he does not appear to have a shadow.
A Link to the Past
Template:Enemy Cannon Troopers look like regular Troopers, wearing blue armor and manning a relatively small red cannon. They do not move from their position, but they do turn to aim at Link, and return to their spot after being knocked back slightly by the recoiling cannon. Their cannon fires spiked cannonballs. They don't do too much damage and despite having blue armour, they only take two attacks from the Fighter's Sword to defeat them.
It's likely that they would have appeared within or around Hyrule Castle or the Castle Tower, and would have been placed in a hard to reach location where they can fire upon Link from one or multiple compass points without fear of retaliation. It's possible they were replaced by Bomb Troopers, as their cannonballs will not fly over Link's head if fired from a high position.
Four Swords Adventures
While the specific enemy does not appear, Soldiers have set up giant cannon defenses in an attempt to defeat the four Links.