Robinhood has become the trading platform of choice for millions of investors around the world in recent years. And as someone who uses the platform, I can attest to the fact that the investment options available for individuals of all trading styles and levels of risk tolerance are virtually endless. 

If you've ever thought about investing in any of the most popular Robinhood stocks but aren't quite sure where to start, let's dive in and look at two of them. Neither stock will be a new name to readers. But the long-term value these companies can lend to a diverse investment portfolio in a variety of environments is exactly what makes them such compelling buys amid rising inflation and an increasingly bumpy market. 

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1. Amazon

Online behemoth Amazon (AMZN -0.21%) dominates the fast-growing e-commerce market, accounting for 40% of such sales in the U.S. alone. Yet it also has a massive footprint in the global cloud computing industry with Amazon Web Services along with an ever-growing list of new ventures like healthcare and grocery delivery. This is a company that investors can buy and hold for a lifetime.  

While shares of the company have increased only modestly in the past year, they have gained a total of about 330% over the past five years. During that same period, Amazon has increased its annual revenue and net income by 184% and 800%, respectively.

Few stocks can rival the level of continuously exceptional performance that Amazon delivers year after year and quarter after quarter. Its incredibly diverse business structure and its ability to consistently succeed in disrupting and expanding in new and existing industries make the company an attractive choice for individuals with a long-term investing horizon.

And if the nearly $3,400 price tag for the stock makes you wince, you might consider investing in fractional shares so you can become a part owner in this tech behemoth for the amount that's suitable to you.  

2. Pfizer 

Pharmaceutical giant Pfizer (PFE 0.10%), now in its 172nd year of existence, has kept its name at the top of global headlines thanks to the stunning success of Comirnaty, the coronavirus vaccine it developed with BioNTech. In its most recent quarterly report, management predicted full-year 2021 revenue of $34 billion for Comrinaty. And the vaccine could continue to have a big impact on the top and bottom lines as the company has agreements stretching into the mid-2020s.

But Pfizer isn't a one-trick pony. It controls a massive portfolio of well-known consumer health brands (Advil, Chapstick, and Nexium, to name a few) and blockbuster medicines like the pneumococcal conjugate vaccine Prevnar 13, blood thinner Eliquis, and cancer drug Ibrance. Pfizer's revenue was up 10% in the latest quarter even without sales of its COVID-19 vaccine.  

Pfizer also trades at a relatively cheap valuation of just 18 times trailing earnings and pays an above-average dividend yield of 3.6%. Healthcare stocks like Pfizer aren't generally known to generate market-beating, share-price returns. But if you're a buy-and-hold investor searching for a stock that can provide consistent value, growth, and a superb dividend for your portfolio, Pfizer is a fantastic choice to consider.