100% concur with my learned colleague.
Here's the deal: You need to show AdComs that you know what you're getting into, and show off your altruistic, humanism side. We need to know that you're going to like being around sick or injured people for the next 40 years.
Here's another way of looking at it: would you buy a new car without test driving it? Buy a new suit or dress without trying it on??
We're also not looking for merely for good medical students, we're looking for people who will make good doctors, and 4.0 GPA robots are a dime-a-dozen.
I've seen plenty of posts here from high GPA/high MCAT candidates who were rejected because they had little patient contact experience.
Not all volunteering needs to be in a hospital. Think hospice, Planned Parenthood, nursing homes, rehab facilities, camps for sick children, or clinics. Check out your local houses of worship for non-clinical volunteer opportunities.
Service need not be "unique". If you can alleviate suffering in your community through service to the poor, homeless, illiterate, fatherless, etc, you are meeting an otherwise unmet need and learning more about the lives of the people (or types of people) who will someday be your patients.