In my office i use Microsoft Essential Anti virus and anti malware. Works good without eating RAM and system speed.
Also my choice is McAfee Security Enterprises v8.8 or Bit Defender or Kespersky Network Workstation v6.
im not using any antivirus at all simply because it is a resource hug and im a advanced user i can distinguish a virus or not . and if i want run a suspicious application i use sandboxie . and it is work . my pc sort of never gets a virus without a antivirus and my windows is never updated . yes even though my windows is original im just lazy to do the update . i afraid that there are update that will enable a telemerery like windows 10
btw i use windows 7 sp 1 without any patches installed