At 4:00pm on July 17, 2007, Robert R. Prechter, Jr. sent out a special Interim Report telling his subscribers to, "....Return to a fully leveraged short position now."
At 3:25pm on February 23, 2009, Prechter sent out his monthly Elliott Wave Theorist, saying in relevant part, "I recommend covering our short position at today's close."
This trade lasted about 20 months and earned 800 S&P points over the course of the trade. Based on a single S&P mini futures contract, those 800 points earned $40,000. Depending on your brokerage rules, about every $4,000 placed in this trade earned $40,000, or about 1,000%.
A once in a lifetime call, or something you can do at home on your own?
Below is a screen shot of my trend following system based on Weekly trading bars. All of the automated trades made from these weekly bars are printed on the chart. You can always click on the chart to enlarge it.

There were seven trades between July, 2007 and February, 2009. Five of the trades were winners and two were losers. Adding up all the points gained by the five winners and subtracting from that sum all of the points lost in the two losers, for the same period that Prechter earned his 800 points on a single short trade, this trend following system gained 766 points.
Unlike Prechter, this system is still Short.
Also unlike Prechter, this system runs on my MacBook Pro.