I used to use Avira everywhere I went or PC's I fixed... but I found that in a few cases it didn't catch everything, was
a bit harder for uneducated folks to use, and you had the pop up that you had to go into safe mode to kill.
So I use Comodo firewall, Avast, Spybot, Adaware, eset online scanner, Spyware Blaster and Spyware Guard, Adblock Plus, iobit Advanced System Care,
and a couple other things setup custom to block intrusions... it's pretty hard to infect me unless I download and run it. Even then, there's levels of security there.
Plus I've got a couple USB sticks worth of other scanners and utilities...