We had an Annual Oral Cancer Walk/Run fundraiser at Penn, organized by the students, for the public, in connection with the Oral Cancer Foundation, for the last 5 years. It has since become a tradition.
Dental Frat parties that are the same every year (Orientation, Halloween, Neon Party).
Certain clubs on campus host the same events every year.
When you start the clinics, almost all the clinic leaders (the 1 head faculty for ~ 20 students) hosts a party at his/her house.