I use Norton Anti-virus Gamer Edition 2009 =P
Loving it, its nice looking, doesn't slow me down, and actually works opposed to what people seem to think.
Norton doesn't suck, which is what everyone thinks. Most of those people are those who used it back in the late 1990's when it did suck so they assume it will forever suck.
The only time I notice its there is when its telling me that its updating, or scanning. The rest of the time I completely forget about it. =P