What is the ideal role of government?

I see lots of debate on Fluther about how the gov’t is ruining this, or should be doing that, or shouldn’t interfere with anything, etc… What do you think the gov’t should do? I see certain important roles of government as public safety, transportation, or (now this could cause argument) correcting for external costs industries impose on society through taxing or fines (like pollution for example). Also, gov’t provides people in charge of overseeing public goods that no one would necessarily step up and provide without proper incentive (like parks or libraries). At a minimum, maximum, or both, how do you see the ideal role of government?