The combination of tax hikes and spending cuts known as the fiscal cliff sits less than three weeks away, yet the market keeps inching higher. For skeptics like me, that's an opportunity to see whether companies have earned their current valuations.

Keep in mind that some companies deserve their current valuations. Life Technologies (NASDAQ: LIFE), for instance, has been barreling higher as lower genetic sequencing costs have boosted demand for the company's products as well as demand for a faster turnaround time for results. Life Tech is also growing by double digits in emerging markets.  

Still, other companies might deserve a kick in the pants. Here's a look at three companies that could be worth selling.

Plus-size valuation
Specialty women's apparel retailer Christopher & Banks (CBK), which also operates CJ Banks, reported a surprise third-quarter profit of $0.10 in late November and shares have been rocketing higher ever since. But is this plus-size valuation merited? My Magic 8-Ball is pointing decisively toward "No!"

The third quarter marked Christopher & Banks' first quarter in the past 10 (yes, 10!) that it's reported a profit, as it's closed roughly 100 stores and pared down its inventory in order to curb expenses and attempt to boost margins. Although I'll gladly give the company credit for turning a profit, it's in the second inning of a nine-inning turnaround campaign and is still projected by analysts to lose money through 2014. Furthermore, over the past decade, bigger discounts and poor inventory management have caused gross margins to fall from a meaty mid-40% range to the high-20% range. That's hardly convincing growth despite what the third-quarter report may have entailed.

This is a stock you don't want to lose your receipt for, because you may want to return it in a hurry once the holiday season is over!

A triple-dog dare
It's amazing, but I always seem to be able to find new and innovative triple-levered ETFs of mass destruction floating around near a 52-week high. Stepping into the batter's box today is the Direxion Developed Markets Bull 3x ETF (DZK).

Let me remind those of you out there who understand that investing in businesses is the best way to prosper that these ETFs are merely extremely short-term trading vessels. Triple-levered ETF adjustments due to daily rebalancing slowly erode their value over time, plus you need to essentially be spot-on with your purchase or sale of these ETFs in order to make any money. Triple-levered ETFs are vulture baskets that prey on new investors who are seeking a quick buck but don't know any better. Don't wind up as food for these vultures and stay far away from the Direxion line of triple-levered funds.

Cliff-diving
To describe General Growth Properties' (GGP) turnaround since its bankruptcy filing as anything less than stellar would be doing it a disservice. The retail REIT that owns numerous malls around the United States has seen a rapid rebound in occupancy rates as big mall-based retail chains have basked in low lending rates to expand their businesses. However, I feel that warning signs are in place that could signal the end to General Growth's amazing run.

The first yellow flag is the simple fact that lawmakers haven't found a way to effectively avoid the fiscal cliff yet. If we do go over the "cliff" and tax hikes go into effect across the board, retailers are going to be hit especially hard, which could negatively impact occupancy rates.

The second yellow flag is General Growth's premium valuation at 19 times forward earnings. Although it boosted its funds from operations beyond consensus estimates on Wall Street, it'll need to turn in some incredible quarters in order to maintain that valuation. We've already seen the warning signs from Gap (GPS 1.13%) and J.C. Penney (JCPN.Q) that customer traffic is slowing, so I wouldn't count on its rapid ascent continuing.

Finally, the possibility of a Simon Property Group (SPG 0.91%) buyout of General Growth has been floating around for nearly two years now, all to no avail. As my Foolish colleague Rich Duprey notes, activist hedge fund investor Bill Ackman would love to see this buyout happen, but Brookfield Asset Management's (BN 1.84%) 40% stake in General Growth makes this a long shot at best, despite the chance of this happening being baked into the stock. 

Foolish roundup
This week's theme can be summed up as succinctly as, "Let's see you do that again!" Christopher & Banks hasn't been profitable on a regular basis in years, all Direxion 3x ETFs require near-perfect timing, and General Growth could be dealing with a major slowdown in consumer spending. I doubt any of these three will be able to repeat their recent results.

I'm so confident in my three calls that I plan to make a CAPScall of underperform on each one. The question is: Would you do the same?