Over the years, Mastercard (MA 1.28%) has done nothing but reward its investors. Since the company's initial public offering (IPO) in May 2006, shares have skyrocketed, rising 12,160% (as of Feb. 3). A $1,000 investment would be worth $122,600 today.That gain is hard to overstate. Even these days, Mastercard continues to put up strong financial results. For prospective investors, is this top financial stock still a buy?Growing the top and bottom lineInvestors will appreciate Mastercard's ability to steadily ...