Some schools require Calculus as a prerequisite - you should check the MSAR (Medical School Admissions Requirements) for information on each school that you are considering applying to. The MSAR is available at many university bookstores, Amazon, or from the AAMC (www.aamc.org).
Otherwise, I'm not sure how useful Calculus really is. It might help you understand Physics a little better - for example, how velocity and acceleration are related - even if you take the trig based variety (which, by the way, is definitely sufficient for admission to medical school).
If you are interested additional math classes, I would recommend taking at least an intro to stats course. A course on research methodology would also be helpful. Even if you never plan to do research yourself, these will both help you understand the medical journal articles you'll be reading. Also, many schools seem to be teaching blocks or courses on biostatistics as part of their curricula - having some stats background will help you understand these courses down the road.