Beanie Babies
There was a time when people went nuts for plush toys called Beanie Babies. These toys came in all shapes and sizes, and gave the buyer the opportunity to fill their house with a range of different colorful and interesting characters. Each of these had their own backstory and everything. Although there was a small surge in sales after whispers that they might be very valuable one day, Beanie Babies are relatively worthless, unless you count the childhood memories, of course.
Modern Comic Books
While vintage comic books can make even the most experienced collector drop double or triple what they would normally pay, modern (new) comic books simply don’t have the same potential resale value. The problem these days is that digitization makes them available at an endless supply. Demand can never increase, because there is an infinite amount of comics that can be bought online. That means that you’re best off collecting something else if you’re doing it already as an investment.