The three I hear most about are TDS, Trojan Hunter, and BOClean.
Myself, I would advice TDS. It is very well made, has a lot of useful features, and is constantly updated. The people at DiamondCS are very dedicated to their products, so you won't ever have to worry about not getting your money's worth.
You could also try out the trial versions. I know off hand that TDS and Trojan Hunter both have free trial versions that you can evaluate.
Everyone has their own experiences and preferences, so giving each program a try will help you choice a program that suits you, not someone else