There are two that immediately come to mind for me. The first, and clear winner, was buying $200 of FB at ~$24, as I was currently running Facebook ads (which u

There are two that immediately come to mind for me. The first, and clear winner, was buying $200 of FB at ~$24, as I was currently running Facebook ads (which ultimately totalled $2M that year) that were wildly successful. It panned out extremely fast, as the rise in stock price had just begun when I purchased. I sold enough to break even when it tripled, sold a bit more around $100, and still have a bit. The other one is somewhat tongue in cheek, but the ultimate ROI was essentially infinity. In 4th grade, I bought a pack of Pokemon cards. I got a Blastoise. I sold it to a classmate for $32. I then bought another pack. It contained a Blastoise. EDIT: To clarify, I purchased that $200 in FB very early in my career, when it was a very major purchase. I own more than the original purchase now, as I bought more later, but I'm speaking solely about the original investment.