Viking's stock took a beating last month, and it has opened up a glorious buying opportunity for investors.The late investing legend Charlie Munger talked about a "fat-pitch strategy," a baseball analogy about waiting for a big, no-brainer opportunity you can take advantage of. When you get that fat pitch, it's a chance to get a home run. In investing, it means potentially securing a massive return.And that's what comes to mind when I think about the recent sell-off in Viking Therapeutics (VKTX 12.78%). Inv ...