hmmmmm, probably the feeding everyone. but it would also severely impact population so idk.

I assumed you would dedicate your life to your family.

Or too much imagination. Let's take your free, clean energy example. 

Is this magical free energy? Or does it require some technical knowledge and skill? Would it be sourced from a central supply like we have today with generating stations? Or could it be modified to a form of inexhaustible battery?

If the free energy weren't constrained to power stations, we would likely see less costly transportation.  This would reduce our cost to go to work, travel, and lower the cost of producing food. 

But if we are reliant on a technical solution, then we would be constrained by the number of people capable of producing the free energy sources. It would take time to produce the free energy devices needed for every person or household.  In the short term, we would have to prioritize who has access to free energy.  And we would want to stop people who would use the free energy from using it for evil purposes.  Fortunately, with free energy, we could afford to keep bombers up in the air and ships out at see constantly.  And we could more cheaply produce those planes and ships. Of course,  we would need more steel and rare earth elements. But the cost of mining would be greatly reduced as transporting tons of ore is otherwise costly, as is the process of turning the ores into usable materials. 

With low-cost transportation, we could drive more, requiring more frequent road maintenace. We wouldn't have to worry about fuel efficiency, so we can drive bigger cars and trucks. Sadly, there would be more traffic accidents and fatalities. We would also need to finance road maintenance differently without fuel taxes. We could, instead, tax energy consumption. Energy would be free, but free energy has externalities that must be paid for.

With lower cost of steel, perhaps we could have rail transport everywhere. Or perhaps public transport would be more affordable to build and operate. Free energy could also mean it's less costly to commute long distances to work. And with the savings, we could have a main residence and a city residence. Of course, we'd have to pay for upkeep of the transportation services. 

With less demand for oil for transportation,  we could afford cheaper and more abundant plastics and chemicals. 

We could also afford to heat and cool every home so that people could comfortably live in the most inhospitable places like Death Valley and Antarctica.  More mining to produce the climate control devices. 

We wouldn't need gas stations. But those can become rest stops for drivers.

We could more afford to build rockets to go to space. By the same token, putting nuclear bombs in space would also be cheaper. Missiles wouldn't be constrained to short range. Troops could be transported much more affordably with free energy and lower cost of food. Weapons and munitions would also be more affordable to produce. Overall, the cost of war would be much cheaper as logistics are generally the costliest part. 

We could also develop AI faster as energy constraints would not hold us back. And everyone could afford to mine bitcoin. Data centers everywhere. Robots. 

Nuclear material would no longer be spent for power. It could go almost entirely for weapons. 

People could also clandestinely grow marijuana, cocaine, opium, and other such things as they could afford artificial lighting and climate control. But just as easily people in cold climates could grow food all year, plants and livestock. 

Desalination would be less costly. 

We could bring back incandescent light bulbs. Heated swimming pools for winter. Every city lit up like Las Vegas. Water fountains everywhere. No need to shut off lighting when leaving a room. We could leave the oven on all the time. Open refrigerators like they have in grocery stores. 

Living underground could be a thing with constant dehumidification, lighting, air purification, and climate control. Boring costs would be lower. Underground prisons could also be a thing. They would be harder to escape. 

Cool stuff, for sure. I wouldn't die for it. In my estimation, it would lead to more centralized control as you only have so many engineers to go around.  Somebody would have to decide what projects get priority for funding and resource allocation. Free energy would increase our natural resource consumption, resulting in more fighting for resources. Extraction would be cheaper, but we would have so many more pet projects to consume those resources. We would replace energy cost with material costs. 

hard to say , maybe to save my wife , daughter or grand daughter 

I don't know, if only everyone had a house and a garden. We also need to tie the unconditional basic income to constant physical activity :)

> ...if it is a ground-level change in society, perhaps it will impact to a point that something will at least disrupt the flow.

I'm thinking, for example, of the example that Martin Luther King Jr. set with his unique speech, which brought about a radical change in American society and beyond. He is still remembered and often quoted today, serving as an example for many young people.