My favorite is still the noctua nh-d15s. It's literally the maximum size you can make an air cooler without blocking features since its slightly offset it doesn't block the first pci-e and since it only uses 1 fan in the center and the heat sink has a slight cutout on the ram side it also doesn't block DRAM. You can keep the fan at stupidly low RPM's even with a moderately OC'd CPU and the center 150mm fan just keeps things cool and completely silent. Should never need more than 800 rpm can run it close to its minimum at 400 rpm and have perfectly fine temps and zero noise. Longer warranty better quality construction. Nope still king of air and you can add a second 120mm fan and still fit it above the fam for even better cooling for extreme OC that rivals custom water and beats many AIO water while being more reliable and making less noise. Just don't move the tower around harshly or u may crack the mobo.
For the price, the i32 is unbeatable. 25 quid on amazon.co.uk. I added a second Arctic F12 PWM fan (the same as the first one that comes with the i32) for an extra 5er... not that it really needed it. Used Arctic Silver 5 (as I have for years). My i7-6700 CPU idles around 30C and never even touches 60C even overclocked 5% on a Z170 board (yes, I'm a very safe overclocker). One year on it's still performing like a champ