NH-D15 every single time :- ). Bigger coolers can run much more silently, though some could object to Noctua's higher prices, the quality is absolutely worth it.
With <105W TDP chips, NH-D15 can run @500 rpm, being virtually inaudible all the time, even during turbo clocks (or when Corona hits denoising).
SilentiumPC, BeQuite, Arctic and Scythe also make great and much much cheaper coolers but I never read cooler reviews so I have no idea which one is best for the money.
I've never bought anything else than Noctua since 2012. Doesn't mean others won't be sufficient, but you might need to read up some tests to see how they compare.
Good measure in tests (I think GamerNexus does it like this often) is accoustic normalized performance, i.e how much is temperature delta @ 20 dB.