Jury DutyThe basis of a fair legal system with judgement by peers. It is already required with punishments for failure to serve without just excuse.I believe our model lies here.
TaxationThe pooling of individual wealth for common purpose and welfare. Avoiding it should be shameful, not good business practice and all avoidance loopholes should be closed. Businesses, instead of sitting on billions in profits should be forced to contribute more. Without the civilization the business can't exist.
ImmunizationA healthy democracy needs a healthy populace. Free choice is always limited when it harms others. Vaccines which truly immunize against serious communicable diseases need to be mandatory.
VotingThe basis of the political system, it is even more essential than jury duty and should be treated as such. Everyone is a registered voter. If you don't show up to vote without a valid excuse you should be fined or face a small amount of jail time, as per jury duty.
All these things are far too important to the common good to be left to individual whim and convenience.Without them a healthy democracy is not possible. Without juries you have no justice. Without immunization you have plague. Without taxation you have no common services, infrastructure, or other projects requiring massive funds and are dependent upon the good will of the few who can afford it, like robber barons and kings. Without voting you have a populatuce able to completely tune out to things that affect everyone's lives. The vocal, often fanatical or extreme few who participate determine the path of the country for all. It becomes a de facto tyranny, an elected dictatorship of the interested. Again, too important to leave to common sense and free choice.
But, except for these four boots to the collective ass, free will should be one of the first common goods protected. Without it, democracy - and life - is meaningless.