The week ends as it began -- on a positive note, with the broad-based S&P 500 (SNPINDEX:^GSPC) rising for a sixth-straight session and claiming another all-time high close.

With no economic data on the table today, investors used ongoing merger and acquisition rumors and deals as fuel to send stocks ever higher. M&A activity is often viewed as a positive for the overall market as it signals businesses' willingness to take on additional risk (i.e., the risk of paying a premium for, and then integrating, a new company). The idea here is that a purchasing company wouldn't buy a competitor if it didn't have good earnings visibility. This implies to investors that businesses expect growth to continue. With plenty of M&A activity in the health-care, technology, and energy sectors of late, it would appear to investors that the U.S. economic hamster is far from tired.

Also, despite lowered growth forecasts in 2014 for the U.S. economy, investors seem pleased with the pinpoint clarity the Federal Open Market Committee offered this week with its interest rate predictions through 2016. While the outlook wasn't anything to write home about, it does give investors a way of planning their investing strategy -- and if there's one thing we know it's that the more transparent the Fed is, the happier investors are!

By day's end, the S&P 500 had risen 3.39 points (0.17%) to close at 1,962.87, its 19th gain in the past 25 sessions.

Topping all individual gainers today was used-car retailer CarMax (NYSE:KMX), whose shares advanced 16.5% after the company reported record first-quarter results.

Source: CarMax.

CarMax saw sales rise 13.3% to $3.75 billion as comparable-store unit sales jumped 3.4% and net earnings per diluted share rose 18.8% to $0.76. Wall Street had projected just $3.57 billion in sales and an earnings-per-share profit of just $0.66. What we're seeing here is the total dominance of the U.S. auto industry from used to new vehicles, and consumers' willingness to spend on a new or used car. As long as lending rates remain near historic lows there's a good chance that CarMax could continue to outrun the Street's expectations.

Source: Hipsxxhearts, Flickr.

Finishing just a hair behind CarMax was Ireland-based global pharmaceutical company Shire (NASDAQ:SHPG), which gained 16.3% after it disclosed it had been the target of an an unsolicited bid from rival AbbVie (NYSE:ABBV) on May 30. AbbVie proposed to purchase Shire for $46 billion, a 23% premium at the time of the offer, which would have been paid via a mix of cash and AbbVie common stock.

While AbbVie pressed the deal as a boon for its long-term growth and an expansive boost to its pipeline, the real allure here appears to be Shire's Ireland headquarters address. Because Ireland's top corporate marginal tax rate is 12.5%, compared to 40% in the U.S., AbbVie could have saved hundreds of millions of dollars in taxes each year by relocating. However, Shire rejected the deal, claiming that it undervalued the company's long-term prospects and denied existing shareholders the opportunity to profit from executing on its strategies. Following today's huge run I'm inclined to stick to the sidelines and wait for a sizable dip in Shire's share price.

BlackBerry Z30, Source: BlackBerry.

Lastly, smartphone producer BlackBerry (NYSE:BB) wiggled its way among the best gainers for a second-straight day, this time adding 7.9%, following positive commentary from Citron Research. Yes, the same Citron Research that is normally on the short-sale side of the picture and attempts to expose poorly run companies. Based on Citron's findings, BlackBerry's tie-ins with the Internet of Things could make the stock worth about $20 per share. While I noted yesterday that I appreciate BlackBerry's tight cost controls and ability to work toward sustainable profitability, I don't see enough in the way of innovative capacity yet to make me a buyer. Until we see products or software that users are really excited about it's probably best to stick to the sidelines.