The pros at investment management giant BlackRock like the look of Pinnacle Financial Partners these days: In the first half of this year, they bought more than 200,000 shares of the largest bank headquartered in Nashville, lifting their stake in Pinnacle to more than 10.1 percent. At the end of 2011, that number was 9.7 percent. Since then, shares of Pinnacle (Ticker: PNFP) have risen more than 20 percent.