Avira for me.
Used Avast for many years, but its detection is not the best.

I found a site that rates all products based on detection results of known & unknown viral strains.. I'll try to dig it up.
Some of you may be rather surprised..

Microsoft Security Essentials

ms security essential

Used to use AVG but it became a piece of crap, luckily Microsoft Security Essentials came out so that's the one for me now too

been using Avast for about 4 months now seems to be doing a good job. Had a nightmare bout 6 months ago when I was tired and downloading Nero or something and clicked something I shouldn't have. Next thing I know - anti-virus is turned off and various crazy things are happening. took me a week of messing around to get back to normal will never make that same mistake again.

I use nod32 but the best is kaspersky or avira

4 me its nod32. using it from 3 years without ny prob

i use the latest kaspersky 2011, it runs really well with real time detection engines although it does seem to slightly cause lag with low end laptops, but runs perfectly fine on my desktop pc

ESET is great

Easier keys than KS

bump bump bump, I added a poll to this thread so now everyone can vote