The majority of stocks ended in the red on Tuesday as falling oil prices and a bleak growth outlook from the European Union worried Wall Street investors. While lower energy prices can actually stimulate economic growth, the larger concern as oil trades below $80 a barrel is the specter of deflation.

Priceline Group (PCLN), along with Michael Kors (KORS) and Halliburton (HAL), stuck out in the bearish market today as three of the stock market’s most severe decliners.

Priceline Group (PCLN)

PCLN stock has been one of Wall Street’s greatest success stories in the last five years, as shares have run up from around $150 a pop to a peak of $1,378 per share. Unfortunately for investors, PCLN stock plunged more than 8.4% today, even after trumping consensus third-quarter sales and earnings estimates.

The selloff was a result of unflattering fourth-quarter earnings guidance, and, as InvestorPlace‘s own Jeff Reeves notes, it was the second such decline of the year for PCLN:

“Priceline stock sold off after it lowered forecasts in August despite strong profits. While revenue has increased by at least 20% a year for each of the last seven years, Priceline is becoming a victim of its own success as investors look forward to big profits despite a massive reach already.”

To me, this sharp move lower says that Priceline shares are currently priced for perfection.

Michael Kors (KORS)

Luxury retailer Michael Kors was another one of Wall Street’s casualties today, as KORS stock cratered 8.4% after its fiscal second-quarter earnings report. Same-store sales, the holy grail of financial metrics in the retail industry, increased by 16.4%, a number that blows stats from its main competitor Coach (COH) out of the water. For comparison, Coach reported a horrendous, 24% decline in same-store sales in its most recent quarter.

So why did KORS stock take a beating, then? Investors were dismayed with North American same-store sales growth, which came in under 11%, as well as management’s ominous preoccupation with weaker mall traffic.

Halliburton (HAL)

Shares of oil services company Halliburton also slumped Tuesday, shedding 5% as oil prices continued to plunge. The price of crude ended around $77 per barrel, a whopping 25% less than its highs above $103 per barrel back in June. HAL stock, in an illustration of its correlation with oil prices, is also down 25% since oil’s peak.

The price of oil is taking a hit this week after Saudi Arabia unexpectedly lowered prices for oil exported to the U.S. in a move viewed by many as an effort to compete with the emergence of America’s domestic shale oil economy. As for HAL stock, CEO Dave Lesar expects shale to actually drive up prices, as cheaper oil discourages shale production and constricts supply.

As of this writing John Divine is long KORS. You can follow him on Twitter at @divinebizkid.