You don't have to just necessarily volunteer at a hospital if you don't want. Do something that benefits society (Habitat for Humanity, March of Dimes, etc...) They want to see that you have a passion for helping others because, well, that's a must for doctors! For example, some volunteer work I've done are: organizing run/walk events to benefit hospital programs, teaching cpr, being a camp counselor for disadvantaged kids. Check with your college for different opportunities.
But what others have said is also important, and that's to do something interesting, fun, or unique from other applicants.
one more thing, whatever you decide to do..try not to do them in the year that you are applying. It will just look like you're trying to beef up your resume (which is probably true if that is the case) You should have done your ECs for at least 2 years, and the more years the better because it shows dedication.