A Screaming Chair was LeChuck's ultimate form of torture for his victims. Using voodoo magic, he would take the bones of an enemy, keep them alive and use them to build a chair.
LeChuck planned to make one from the bones of Guybrush Threepwood and Wally B. Feed, so that every morning he could sit on it and would hear them scream.
This is mentioned by LeChuck in Monkey Island 2: LeChuck's Revenge.