When investors have some idle cash to put to work, most of the time, they'll look for stocks they don't already own. And for good reason. More diversification is a good thing.
It's not always easy to do, though. Sometimes the best stocks for a particular investor are already in their portfolio. In these instances, it's not wrong to buy more of a great name you're already holding.
With that as the backdrop, here's a rundown of three fantastic stocks you may well already own, but can safely double up on, especially following each ticker's recent weakness.
1. Microsoft
Microsoft (MSFT 1.32%) may be an aging name contending with the downside of its sheer size. But this old dog's still got plenty of fight left in it. Last quarter's top line of $77.7 billion was up 18% year over year, with $30.8 billion of that being turned into net income. If the software giant is supposed to be past its prime, somebody clearly forget to give Microsoft the message.
This continued growth is rooted in two factors that aren't apt to unravel anytime soon... if ever.
The first of these is its sheer dominance. Not only does the company remain a powerhouse within the personal productivity software space, its Windows operating system is installed on roughly two-thirds of the world's computers, according to numbers from Statcounter. This degree of resilient market penetration suggests Microsoft has become a permanent fixture within the personal computing landscape.
And the second factor behind the company's enduring strength? Its Windows operating system actually steers consumers and corporate clients alike to other Microsoft-made products and services like its Bing search engine, LinkedIn, and even its Azure cloud computing platform.

NASDAQ: MSFT
Key Data Points
This brute strength obviously hasn't helped investors much of late. While shares haven't exactly performed poorly since July, they've not made any net progress either, missing out on the broad market's gains during this stretch.
Blame growing worries about its artificial intelligence (AI) ambitions, mostly. Although nobody denies it's doing great things on the AI front, investors are increasingly concerned that Microsoft is also competing with its own artificial intelligence partner OpenAI. It's still simply spending a ton of money on artificial intelligence as well, at a time when investors are starting to question most AI stocks' steep valuations; many of these companies have yet to produce the sort of ROI on these investments that the world was hoping to see by now.
Now take a step back and look at the bigger picture. This is Microsoft. There's a reason the analyst community still contends the stock's worth $631.80, which is 28% above shares' present price. That reason is the unstoppability that comes with its sheer size and its must-have offerings.
2. Coca-Cola
It's been an unusually tough year for Coca-Cola (KO +2.44%) shareholders. Although the stock's bounced back somewhat from its midyear lull following a couple of red flags in recent earnings reports (the second quarter's total sales volume fell slightly year over year, for instance, following a warning with its first-quarter report that then-new tariffs could take a toll on its bottom line), it's still trading below April's high while the rest of the market isn't.
As is the case with Microsoft, though, it's not like Coca-Cola is in any real existential danger. It's the world's biggest, best-known beverage name for a reason, after all.
That reason is, over the course of its 139-year existence, it's gotten very, very good at marketing. It's more than a mere drinks company -- Coca-Cola is a lifestyle brand, with its flagship soda's name and logo appearing on everything from clothing to Christmas ornaments to home decor. That's powerful.
Image source: Getty Images.
This durable marketability is only part of the reason you might want to buy Coca-Cola shares sooner than later, though, and not even the best reason. Far more compelling is the fact that you can step into this stock while its forward-looking dividend yield stands at a solid 2.9%. And that's based on a dividend, by the way, that's now been raised for 63 consecutive years.
3. Visa
Finally, add credit card powerhouse Visa (V +1.42%) to your list of stocks to double up on here, if you're struggling to find a new name you like well enough to add to your portfolio.
Anyone keeping long-term tabs on this company likely knows last quarter's top-line growth of 12% is a bit above long-term norms, boosted by the swell of cross-border payments the company is now able to facilitate, and has reason to. As Visa Direct's Europe chief Anastasia Serikova noted earlier this year, "Cross-border payments have seen substantial growth due to the increase in international trade, global workforce mobility, and remittances, with total global cross-border payment flows growing at around 9% (CAGR) annually."

NYSE: V
Key Data Points
This growth engine isn't apt to sputter to a stop in the foreseeable future, either. Serikova adds, "With the increased mobility of people, goods, and services across borders, total cross-border payments are projected to reach $250 trillion by 2027, a $100 trillion increase from 2017."
Then there's the other, largely overlooked reason to scoop up some/more shares of Visa in the wake of its pullback from its June peak. That is, while worries about its growth prospects, regulatory headwinds, competition, and the stock's steep valuation are all credible, what's not being priced in is Visa's potential upside from the use of artificial intelligence technologies.
Whereas some institutions are utilizing AI simply for the sake of using it (without any clear positive impact), a complex, digitally focused, data-rich company like this payment middleman can actually do something constructive with artificial intelligence. This includes AI-powered customer service agents, data analysis, and cybersecurity in an industry that's highly vulnerable to fraud, just to name a few. It's actually a pretty big deal that's not being fully reflected in the stock's price.