I vote for avast! Last time I use AVG, that's my second choice.

Haha... last time, many years ago I use norton. Looks profesional but quite useless actually. Sometimes or I should say most of the time, it can detect a virus but it can't do anything and at last it got infected and got crazy. Maybe it's just for my computer... And I recently, tested between avast and norton on two similar computer. I loaded a critical virus and avast detected the virus before the virus can be saved into the HDD. But norton did not respond to the virus until 20 seconds later.