Emsisoft Anti-Malware Free (Previously A-squared Free)
Full user review
"Seemed to work for me"
Found a great many malware files, much more that Super Antispyware or AVG.
Deep scan took about 6 hours.
I used this in conjunction with RKill to recover from the "System Fix" Trojan, which is really nasty. It was the latest 30-day free trial (not actually free) version. It found and removed 78 malware files while Super AntiSpyware (free) and AVG (free) found only a handful. I'll probably buy it at the end of the 30 days.