Hitman Pro is a freeware tool that combines a number of powerful anti-spyware programs in one integrated solution. In nearly all anti-spyware reviews, the conclusion is that none of the anti-spyware programs removes all spyware. A combination of two programs is recommended.
This is exactly what Hitman Pro does: it combines Ad-Aware SE, SpyBot Search & Destroy, Spy Sweeper, Spyware Doctor, CWShredder, Spyware Blaster, NOD32, Sysclean package. Most of the included programs are freeware.