Berkshire Hathaway (BRK.A 0.33%) (BRK.B 0.27%) CEO Warren Buffett is arguably in a class of his own when it comes to investing legends. Since taking the helm of Berkshire Hathaway in 1965, the Oracle of Omaha has led his stock to an average annual return of 20%. Taking into account the 20% year-to-date gain for Berkshire's Class A shares (BRK.A), shareholders have seen Buffett generate aggregate returns of almost 3,400,000% in 56 years.

Although Berkshire Hathaway has a relatively large portfolio filled with four dozen different securities, Buffett has never been a big fan of diversification. As a result, only a small number of holdings comprise the bulk of Berkshire Hathaway's $206.4 billion in unrealized gains, as of this past weekend.

Based on the cost basis of Berkshire's major holdings (outlined in the company's 2020 annual shareholder letter), the following five stocks have netted Buffett $181.1 billion in combined unrealized gains (about 88% of all current unrealized profit), not including dividends paid. 

Warren Buffett at his company's annual shareholder meeting.

Berkshire Hathaway CEO Warren Buffett is all smiles with his company sitting on over $206 billion in unrealized gains. Image source: The Motley Fool.

Apple: $101,764,676,001 in unrealized gains

Easily the best investment of Buffett's tenured career is Apple (AAPL 0.38%). Even after modestly paring down his company's stake in the tech kingpin, Berkshire Hathaway still owns 907,559,761 shares at a cost basis of $34.26 a share. With Apple closing last week at $146.39 a share, the Oracle of Omaha and his team are sitting on close to a $102 billion unrealized gain.

Investors certainly shouldn't look for this stake to be reduced any further anytime soon. That's because Buffett views Apple as Berkshire Hathaway's "third business." It's a globally recognized brand with an exceptionally loyal following, as evidenced by the mammoth lines outside of its stores anytime a new product hits the shelves. And, as you're probably aware, the iPhone is the dominant smartphone by market share in the U.S.

In addition to Apple being a product innovation juggernaut, CEO Tim Cook is overseeing a steady transition toward services. By emphasizing various subscription-based platforms, Apple can reduce some of the revenue lumpiness associated with tech replacement cycles and likely boost its operating margins.

A final reason Buffett isn't bailing on Apple is the company's generous shareholder return program. Though some of you might be scratching your head given that Apple's dividend yield is "only" 0.6%, the $0.88 base annual payout is closer to 2.6% of Berkshire Hathaway's cost basis. Tack on Apple's aggressive share repurchase program and you have a very shareholder-friendly company.

A bank teller handing cash to a customer.

Image source: Getty Images.

Bank of America: $24,530,235,143 in unrealized gains

There's no industry on the planet Buffett loves more than bank stocks -- and there's no bank stock Buffett favors more than Bank of America (BAC 0.55%). Berkshire Hathaway owns over 1.03 billion shares of BofA with a cost basis of $14.17 a share. This works out to an unrealized gain of just over $24.5 billion, based on where BofA shares closed this past Friday, July 16.

Buffett has always been a big fan of playing the economic numbers game, which is exactly what he's doing with Bank of America. Since the U.S. economy spends a disproportionate amount of time expanding, relative to contracting, bank stocks like BofA should benefit from stronger loan origination and higher net interest income. The Oracle of Omaha is fully aware that recessions are a natural part of the economic cycle, but he fully understands that the long term strongly favors optimists.

More specific to the business, BofA stands to benefit from eventual interest rate hikes by the Federal Reserve. Bank of America is the most interest-sensitive of all the big banks, with the company noting in the June-ended quarter that a 100 basis point parallel shift in the interest rate yield curve would net it an extra $8 billion in net interest income over the next 12 months. 

With BofA pushing digitization initiatives and bolstering its dividend program, it's far likelier that Buffett ups his stake in the company than sells a single share.

A person holding an American Express gold business card.

Image source: American Express.

American Express: $24,488,160,264 in unrealized gains

Whereas the gains racked up in Apple and BofA have come within the past couple of years, the nearly $24.5 billion in unrealized gains in credit services behemoth American Express (AXP -0.26%) have been built up over the past 28 years. With a cost basis of right around $8.49 a share, Buffett's patience has paid off in a big way with AmEx.

Similar to Bank of America, American Express is a cyclical company that benefits from the aforementioned numbers game. If the U.S. and global economy are expanding, consumers and businesses are more likely to spend more, thereby helping boost payment processing revenue and profits. Keep in mind, though, AmEx is a double dipper. In addition to processing payments, it's also a credit services provider. This means it can generate growing amounts of fee revenue and interest income during long-winded periods of expansion.

Another facet to AmEx's success is the company's ability to bring in affluent clientele. The well-to-do are far less inclined to alter their spending habits when minor economic disruptions rear their heads. As a result, AmEx isn't as likely to be hurt by credit delinquencies as some of its lending peers.

With Berkshire Hathaway an American Express shareholder since 1993, I don't foresee Buffett or his team selling shares anytime soon.

Two friends clanking their Coke bottles together while seated and chatting outside.

Image source: Coca-Cola.

Coca-Cola: $21,262,000,000 in unrealized gains

Speaking of tenured holdings, no stock has been a fixture in Buffett's portfolio for longer than beverage giant Coca-Cola (KO 0.09%). With a cost basis of a fraction under $3.25 a share, Buffett and his team have piled up almost $21.3 billion in unrealized gains by owning Coca-Cola since 1988.

Like Apple, we're talking about a company with insanely strong branding and brand recognition. Coke products are sold in all but two countries worldwide (Cuba and North Korea), and it has more than 20 brands in its product portfolio generating at least $1 billion in annual sales. Coca-Cola enjoys the best of both worlds, with 20% of the developed market cold beverage share (i.e., highly predictable cash flow) and 10% of emerging market cold beverage share, which represents a higher-growth opportunity over the long run.

Beyond geographic diversity, marketing is a big reason for Coca-Cola's success. The company has not been shy about turning to social media and well-known ambassadors to represent its brand, and it has clear holiday tie-ins that go back decades.

Considering that Berkshire Hathaway is netting almost a 52% annual dividend yield based on its original cost basis for Coca-Cola, there's absolutely no incentive to sell this position.

An accountant checking financial statements line by line with the help of a calculator.

Image source: Getty Images.

Moody's: $9,076,258,024 in unrealized gains

While Apple singlehandedly takes the crown for generating the highest unrealized return in nominal dollars for the Oracle of Omaha, credit ratings agency Moody's (MCO -0.27%) might well be Warren Buffett's greatest investment on a percentage basis of all time. Berkshire's cost basis is $10.05 a share following Moody's spinoff from Dun & Bradstreet in 2000. Moody's closed this past week at almost $378 a share -- good enough for a 3,661% return and nearly $9.1 billion unrealized gain.

One thing keeping Moody's busy is historically low lending rates. With the Federal Reserve standing pat for as long as possible on interest rates, businesses haven't been shy about issuing debt to hire, acquire, innovate, or even buy back stock, as in Apple's case. With so much corporate debt issued, Moody's has been active evaluating the debt landscape.

Equally exciting has been the generally heightened levels of market volatility and economic uncertainty since the beginning of 2020. Though Moody's is best known for its credit ratings operations, its fastest-growing segment tends to be analytics. As long as deep levels of uncertainty exist, Moody's Analytics has double-digit annual growth potential.

As with Coke, Buffett's patience has resulted in an insanely high yield on cost with Moody's. Despite a 0.7% nominal yield, Berkshire Hathaway is netting an almost 25% yield annually, based on its initial cost basis.