Bit defender is what i use and have never gone back, is incredibly light weight as well as hourly updates, i have pretty much used or played with most other anti virus but none compared to bit defender
is very cheap too compared to most plus you get 3 pc's protected for a year
I voted Kaspersky because it has several features, such as how many Kaspersky users have used the application before, and if it is a trusted rating. The only downside is the slow scanning.