What are the most likely, realistc, and feasable scenarios for the catastrophic collapse of our economy?

I don't think the world would totally collapse, unless there was all out panic/war. The global economy is so well intertwined these days that it would be very difficult for any one country's economy to bring down the world economy, save a few. China, U.S., and U.K. would have a detrimental impact to the world economy. But as I said, it would be very difficult for any of those economies to completely fail. Consider consumer expenditure on an annual basis. Consumers generally have a certain amount of money to spend on goods and services.. Consumers are always going to spend, and as long as there are places of businesses to sell those goods, consumers will continue to buy. There are certain categories/products that are necessities and are almost immune to economic impacts due to the fact that they are necessities.

However, if the world economy were to collapse, it would require a big event to cause that collapse. The fall of the U.S. government/nation would certainly have a large impact globally, since most countries rely on the U.S. for food, technology and various other resources. At which point hyper-inflation would be rampant, prices of goods&services would rise dramatically and businesses would collapse. The strain would cause a dominoe effect. However, it wouldn't be permanent. The global economy would reset itself once it settles say in 1-2 years following the economic collapse. Global prices would drop, employment would rise and inflation would reset. We would more than likely turn towards bartering as a form of exchange instead of currency and I'm sure the gold standard would be reinstated.