Which Antivirus & Antispyware software do you think is the most effective?

I am using AVG Antivirus and AVG Antispyware now, but I don’t think they are the most effective. I am looking for the most effective free one.

By the way, this is not a question and everyone can just express their opinions here.

Please also state why the software that you have chosen is in your opinion, the best.

Happy Discussing! 🙂