I have read that some slave owners would drive nails into a barrel and put the slave to be punished into the barrel and roll them down a hill.
Thumbscrews were also used as a device to punish slaves. This device was also used in the medieval times as well as a form of punishment. This device was like a vice but it had sharp spikes inside of it. The thumb (or sometimes even a toe) was placed in the vice and the thumb would then be slowly crushed.
Punishment was not always physical but mental as well. For example, punished slaves would have a loved one such as a husband or wife, or child sent away never to be seen again as a form of punishment. Also, slaves were punished by whipping their children in place of them.
The previous posts were quite accurate. The use of rope to hang slaves was also something of use, and later on, the use of the gun to repress slaves could be seen of use. In some slave narratives, to punish runaway slaves who were caught, using an axe to cut off a slave's big toe was something of use. Slave owners were not lacking in the use of weapons to punish and control slaves. They resorted to emotionally cruel techniques. The separation of family members in front of one another could be seen as an instrument to punish slaves. The willful hurting of another family member in front of another as a means of getting what the slave owner wanted could be seen as an instrument to punish slaves. Finally, the "choosing" of different slaves to work in the homes of the master in the hopes of dividing and conquering over the slave population could be seen as an instrument to punish the hopes of collectivizing against the master.
One of the most common was whipping, whether it was the more severe version akin to the flogging found in the British Navy which could eventually kill a man or the use of a whip or a bull whip to goad a man to work harder or to demonstrate power over them.
There were also times that slaves were fitted with heavy metal collars used to keep them in line as well as to serve as an actual restrictive device when connected to a chain.
One thing that was not considered a punishment in the strict sense but perhaps was even more horrible was the relatively constant practice of rape by male slave owners of their female slaves. It was something considered quite normal with many slave owners and the children of these rapes were also considered slaves unless the owner saw fit to "free" them.
Slavery was such a cruel act of human beings to mistreat others so badly that there are instruments to be defined. The first one hat comes to mind is the whip. It was soaked in water and slashed across a slaves back. By soaking the leather it made it bite deeper into the slaves skin.
The steel collar was welded onto the slaves neck, or attached to it and then clamped shut so that the slave himself could not remove it. The slave then ahd chains attached to it and he was connected to other slaves, treees, or any object that could be used to secure the slave.
Leg irons were often attached to slaves so tightly that they dug into the skin and caused infection. It was not that uncommon for a slave to develop gangrene from an infected area.
A yoke was also placed across the back of a slave with his arms extended forward and handcuffed to the front. This caused extreme tension on the slaves neck and shoulder muscles. If left in the device too long the slave would suffer permanent injury and deformity.