Whether it's bear markets, shifting legislation, or an unstable macroeconomic environment, there are plenty of reasons an otherwise-stable company might see its stock stumble temporarily. Pfizer's (NYSE: PFE) shares are down by 20.3% in the last 12 months, and if you're willing to hold on to them for the long run, this stock is a great option for buying on the dip to gain a passive income stream.