Among the biggest stocks (as measured by market cap) are Exxon Mobil (XOM), Microsoft (MSFT), BHP Billiton Ltd. (BHP), Walmart Stores Inc. (WMT) and Apple (AAPL). And as low-risk investors jump into the stock market, these companies will be first on the radars of those with conservative strategies.

You may ask “Why would very conservative investors even bother with stocks?” Well, because the safest investments are barely keeping up with the rate of inflation right now. Large, low-risk blue chips like Exxon, BHP, Microsoft, Walmart and Apple may not be sure things — but even a bad stock investment is easier to stomach for many investors than just watching your money slowly eroded by the march of inflation.

Of the over 5,000 stocks that I track in my free Portfolio Grader database, the five biggest companies are Exxon Mobil (XOM), Microsoft (MSFT), BHP Billiton Ltd. (BHP

), Walmart Stores Inc. (WMT) and Apple (AAPL). These companies are so big that they need no introduction — but let me give you my opinion on each of them:

Exxon Mobil (XOM) has had a tough year and is about flat from where it was trading just 12 months ago. After what had been an incredible run that included some of the biggest quarterly profits in history, the company was not able to maintain that growth pace. I don’t see the company returning to its former glory any time soon and that makes it one of the big blues to avoid right now.

Microsoft (MSFT) has been on the opposite track as XOM. In the last 12 months the company has seen strengthening fundamentals and an upward moving stock price. With strong fundamentals and nice buying pressure, this stock will likely see a good chunk of the new cash that is flowing into the market.

BHP Billiton Ltd. (BHP) stock has succeeded where XOM has failed. The company has been a nicer performer over the last year and has been a decent buy for investors. However, past performance in this case is not an indicator of future success. Right now the company is having some difficulties with sales growth and buying pressure. If you were thinking about adding this $225 billion company for some safety, I would hold off and see how the next few quarters go before diving in.

Walmart Stores Inc. (WMT) stock has seen some solid price jumps in the last year on analyst upgrades and other news. However, I don’t see as powerful a move coming for Walmart as one would expect from a blue chip surge. Analysts have stayed firm with their expectations for upcoming earnings and the company has a history of surprising Wall Street by about 5% or so. I don’t see this company as one that will grab investors’ attention this earnings season and as such you should instead look to buy other conservative stocks.

Apple (AAPL) shares hit an all-time high this week on news that it is considering developing a phone for Verizon. Currently you have to be an AT&T member to enjoy Apple’s iPhone, but an expansion into this customer base would be huge for the company. While it isn’t a done deal, this is just the next in a great run of good decisions for the company. I know the $235 share price can be scary, but when you have a great company like this that consistently beats analysts expectations by 50%, 60% or 70%, you have a solid investment.

Many Federal Reserve watchers had thought that the central bank would begin to raise interest rates to protect against crippling inflation beginning in 2012. But because the U.S. economy is reliant on an artificially-low Federal Funds and because a hike in interest rates could potentially add a trillion dollars to the cost of servicing the U.S.’s massive debt, interest rates should remain low for a while.

This should help give the stock market rally some legs since investors will have no choice but to abandon miniscule bond returns and anemic Treasury bill yields and put their money to work in stocks. But that doesn’t mean investors are getting aggressive. This new money is coming from the “safety” of bond and T-Bills and it’s likely that this money will also seek out the “safest” stocks. This means good things for blue chip stocks as they are typically perceived as safe bets.

As you can see, Apple and Microsoft are by far the best bets among these five behemoths. Walmart, BHP and Exxon may be low risk but they will fail to deliver any substantial returns as well.

Louis Navellier owned shares of AAPL in personal or client portfolios as of this writing.