Using a 'pigtail' coil, a brewer pulls a sample of fruit beer from a 'bright' tank.
A bright tank is a dish-bottomed pressure-rated temperature-controlled tank used to hold beer in preparation for packaging. The term "bright" refers to "bright beer," beer that has been rendered bright (clear) by filtration, centrifugation, fining, and/or maturation. [...] As many craft beers are not filtered or clarified, the beer sent into the bright tank may not be bright at all.—The Oxford Companion to Beer
But beyond artistic drama, why that 'pigtail' coil?
The beer in the bright tank was fully carbonated, under pressure. A pigtail's long length of narrow-gauge stainless-steel created resistance to the beer flow along its length, at a rate almost equal to the pressure in the tank.
If the brewer had simply opened the sample valve without this restriction tubing attached: good luck! With no resistance to keep the carbonation dissolved, the beer would have spewed out as foam. But with it: voila! The sample was poured with a minimum of foam, most of the CO2 dissolved in the beer as the brewer had intended. (By the way, it's the length which accomplished this, not so much the 'pigtail.' The coil was there to keep the distance from the valve to spout within the brewer's arm's length.)
As seen at Jailbreak Brewing Company in Laurel, Maryland, on 26 July 2014.
Pro tip: the 'actual' name for this is a proof coil sampling valve. But saying pigtail is more fun.