Many times a day in this country (and many more times worldwide), someone feels the sting of two needles pierce his or her skin, followed by a hair-raising, five-second jolt of electricity. Taser weapons are in use by more than 16,000 police departments in more than 100 countries, and they've changed the business of policing at a fundamental level. Cops reduce injuries to themselves by choosing to "tase" someone rather than getting into a fight, and sometimes a suspect who might have ended up shot rides the lightning for a few seconds instead.The electrifying trend took off from Scottsdale almost 20 years ago, after two local brothers, Rick and Tom Smith, bought the rights to an early form of the weapon. Starting from their garage in 1993, the Smiths made the product marketable — in part by abandoning a propulsion method for the darts that used gunpowder, going instead to an air-powered model. By the 2000s, Taser International had turned into a powerhouse with high profits and soaring stock prices. The company's seen ups and downs in finances and public opinion — critics blame Tasers for the deaths of hundreds of crime suspects — but its revenue was up this spring following sales of its new "X2" stun gun. One of the Valley's most notable exports, in other words, is pain.