50 months ago
i5 6600 with a gtx 960. Not planning on overclocking
Make sure it's an i5-6600, and not an i5-6600K. Intel stopped bothering to ship stock coolers with the i5-6600K and i7-6700K, because 99% of users just replaced the stock cooler anyways.
Well you couldnt OC even if you wanted to unless you can crack the CPU, and no a cooler isnt required but if you want it to be quieter and cooler then get a sub-$40 (£30ish) cooler
If you're using a 6600 non-k CPU, you don't need a cooler as the CPU comes with one in the box.
To be clear, yes a cooler of some kind IS definitely required. You can use the one in the box though if you are not buying a K series CPU.