I like leaning on Nobel Prize winning ideas to ensure good contributions to the list. So, I bring you the Nudge, courtesy of Richard Thaler (and, to be fair, others before him). This is an idea grounded in what is often called paternal libertarianism, or the idea that one allows people to retain their choices, but one also shapes decisions by presenting them in ways that will lead to the "better good" through default choices that people tend to make.
A nudge is thus a choice presentation that is likely to produce a specific and predictable outcome from the chooser, without them feeling as if 1) options were taken away or 2) they were manipulated. Often, these are simple framing effects. For example, a nudge toward more organ donation is to have people opt OUT of being an organ donor rather than opt IN. People tend to not check boxes for things, and so here, they stay IN the program. Other nudges include food placement in school cafeterias, donation solicitations, and others.
And, there is always the nudge found in some men's rooms, in the form of a target to aim at in the urinal, to promote greater cleanliness! For more on that, see: https://wapo.st/2mnRagY