Im pretty sure kaspersky is. Or Nod32 I think is a little bit worse.

For free virus scanners I have only used AVG Free, and it does an alright job. I have tested it against Nortan, and AVG didn't find any virus, while Nortan found a few and one was actually a trojan. Though some scans may be misleading because they can sometimes consider cookies as adware, or programs you have as viruses even though they aren't.