It depends on the desired effect. For example, lavender oil is often used for relaxation, while peppermint oil is a great choice in helping to decrease pain, while eucalyptus oil works well as a decongestant. There are many different essential oils that can be used for aromatherapy, each with its own unique set of benefits. Some of the most popular essential oils include lavender oil, peppermint oil, eucalyptus oil, tea tree oil, and citrus oil. Each of these oils have a unique set of properties that can benefit the body in different ways.