Teachers - They are so crucial to growing the minds of our youth, yet they are so grossly underappreciated, undercompensated, and underfunded for resources.
Nurses and PAs - The MDs get so many accolades but it's usually the nurses and PAs that handle the heavy lifting when it comes to patient care.
Entertainers - Unlike my first two, many of these are paid handsomely. That being said, think about what it does for your mood and overall wellbeing to enjoy some entertainment. From movies and music to comedies and art, these creative and talented people provide a service to mankind that helps our minds recharge and enjoy.