Answer:
Everything can make someone unconscious if administered in the wrong way. Even something that is considered by most people as safe- such as drinking water. Although, nothing is a poison without a dosage. Some common chemicals that were used to make people unconscious were chloroform and diethyl ether. Chloroform can be made simply with bleach and acetone. But remember it is dangerous to use without the known dosage and there may be some toxic ingredients that will spawn from the mixture such as chlorine.