m0demb0y
I use BitDefender Free edition. They consistently rank among the highest in detection rates and it uses very little resources compared to some others. Never been nagged or even gotten a marketing email from them.
Bitdefender user here, by far the best one I've used, but I'm a paid user and no issues for like 5+ years.
+1 "uses very little resources"
I actually tried and uninstalled the following...
AVG, Avast, Kaspersky, Trend Micro, Norton and ESET