You should be buying oil and natural gas stocks regardless of where oil and natural gas prices are headed, James Cramer said on his "RealMoney" radio show Tuesday.

Four days of falling oil prices have begun to lull some people into thinking maybe there isn't an energy shortage, Cramer said. But that's "wishful thinking," he said.

Nevertheless, suppose Cramer is wrong, he said, and prices go back down to $55 for oil and $7 for natural gas. You should still be buying oil and gas stocks because the fund managers of the best-performing mutual funds are nearly all overweight oil and gas, and, for the most part, they believe, as Cramer does, that oil and natural gas are headed higher.

So, at the end of the month, when the lists of top-performing funds are published, those funds will receive a lot of new money, which will be invested right back into oil and gas stocks. Even if Cramer is wrong about where oil and gas prices are headed, he said, you could still get bailed out by the top-performing funds' buying of energy stocks.

"I believe you should buy the stocks just for that," said Cramer. "You have been given still one more opportunity to get into oil at prices I don't think are going to stay. So, why not take advantage of it? Why not buy more?"

Cramer's "Danger Zone" stock for Tuesday was Delta Air Lines ( DAL - Get Report). Cramer believes Delta's common stock will be wiped out in bankruptcy. "If you own Delta, you should sell it because it's not worth anything," he advised. Delta traded at 81 cents Tuesday afternoon.

A caller asked about Zimmer ( ZMH). Cramer said he is concerned after reading Melissa Davis's "chilling" article Monday that said the Japanese government may ask Zimmer for a price rollback of up to 8% for its orthopedic implants. If that plays out, said Cramer, Zimmer's numbers are too high. Cramer said he would wait until tomorrow or the next day, at least, until everybody knows the news and then look for a buying opportunity.

An emailer wanted to know what he should do with Best Buy ( BBY - Get Report) after it reported a "not-so-great" quarter Tuesday. Cramer said that historically, buying Best Buy on "breaks" like today has been profitable, and he doesn't think this time will be different. However, there could be an analyst downgrade tomorrow or some spillover selling. So, he "would be a buyer tomorrow, not today," said Cramer. Best Buy shares were trading down 10% to $45.36 Tuesday afternoon.

Another emailer asked about BJ's Wholesale Club ( BJ). Cramer said retail is not a favorite sector of his right now. Nevertheless, he believes BJ's "should be bought."

In response to an email about CVS ( CVS - Get Report), Cramer said it was "good" and tends to do well in tougher economic times. However, he would rather own Walgreen ( WAG), which is "best of breed."

Cramer is not a fan of Finish Line ( FINL), adding that the company "missed the quarter," and he is not a fan of the shoe business in general.

Cramer said Wal-Mart is "still not a buy," but it "will be when we have a recession."

In response to questions about teen apparel retailers, Cramer said he does not like Pacific Sunwear ( PSUN), Hot Topic ( HOTT), Abercrombie & Fitch ( ANF - Get Report) or Aeropostale ( ARO). He does like Urban Outfitters ( URBN - Get Report), but cautioned Urban is "high multiple retail," and "I don't want to own expensive stocks here." He also said Zumiez ( ZUMZ - Get Report) "will have growing pains" as it is early on in its expansion, but he likes the stock.

In response to a question about Dynegy ( DYN), Cramer said Dynegy is "OK," but " El Paso ( EP) is better."

"Almost any energy company ... is better than any retailer," Cramer added.

In response to a question about Smith & Wesson ( SWB), Cramer said the company recently issued stock, which led to its fall to about $4.50 from $6. With that "overhang" gone and with the company no longer facing litigation risk, the circumstances have changed for the better, he said, and he would be a buyer.

A caller asked about Northrop Grumman's ( NOC) announcement of a $124 million Navy contract. Cramer said the contract is simply too small relative to NOC's size to be a reason to own the stock. However, Cramer is a fan of defense contractors in general like Northrup, General Dynamics ( GD - Get Report) and Alliant Techsystems ( ATK).

Finally, Cramer said he would "hold on" to Skyworks ( SWKS). As a result of Nokia's ( NOK) "better-than-expected" quarter, Cramer said he believes people are swapping out of Skyworks and into RF Micro Devices ( RFMD), which supplies Nokia. However, Cramer said he would want to own Skyworks because it supplies Motorola ( MOT), which he likes better than Nokia, adding that Skyworks is "largely a fourth-quarter story."

At the time of publication, Cramer was long Alliant Techsystems and Motorola.

James J. Cramer is a director and co-founder of TheStreet.com. He contributes daily market commentary for TheStreet.com's sites and serves as an adviser to the company's CEO. Outside contributing columnists for TheStreet.com and RealMoney.com, including Cramer, may, from time to time, write about stocks in which they have a position. In such cases, appropriate disclosure is made. To see his personal portfolio and find out what trades Cramer will make before he makes them, sign up for Action Alerts PLUS. While he cannot provide personalized investment advice or recommendations, he invites you to send comments on his column by clicking here. Listen to Cramer's RealMoney Radio show on your computer; just click here. Watch Cramer on "Mad Money" at 6 p.m. ET weeknights on CNBC. Click here to order Cramer's latest book, "Real Money: Sane Investing in an Insane World," click here to get his second book, "You Got Screwed!" and click here to order Cramer's autobiography, "Confessions of a Street Addict."