If you want free one, can get Avira, only thing is that it will be advertisements. it is the best free one available.
Very well balanced across detection rate and speed. Buying price is quite reasonable.
If not, go for Norton, trial and proven many years.
Can consider Kaspersky as well.
Anyway, do not just look at one year of antivirus comparison chart from AV-comparatives. It might have the best scores this year, but if their development team is not good enough, the next year update might be a lousy one.
Norton actually went through this stage during 2007 where its 207 Norton EXTREMELY slow such that many users stop using it.
What I will say is that Avira, Kaspersky and Avira and scores very high throughout their years of development, thus you should really consider these 3 brands.