According to Keirsey, Santa Claus is most likely ESFJ.
"The Guardian type known as the Provider (ESFJ) is sometimes known as the "Santa Claus" personality since they are generally well-liked and notice whenever situations become "naughty or nice." They provide for the welfare of many and usually show well-developed social skills. They are happiest in positions where they need to deal with people. It is not uncommon to find them in health care, as a physician, nurse, or respiratory therapist. They also can be attracted to the field of education, social service, or religion. In business they may be a retail owner, receptionist, real estate agent, or sales representative. The common theme is their service to others. Says Alice, "As a teen I did hospital volunteer work, but decided I preferred education so got my teaching degree. I've been teaching elementary school for 5 years. I love helping children to learn.""
Keirsey' PersonalityZone - Temperament and Your Career