Don't really use any extra on-demand scanners on my own systems since I never get infections. My brain and Avast pretty much gets everything.
But when it comes to removing malware from my customers systems, I prefer MBAM since the majority of malware infections are rogue security applications.
Most Anti-virus software have problems detecting rogue applications.
MBAM scans quickly and can remove almost all of the rogue applications that other scanners can't detect.
Of coarse MBAM doesn't detect many viruses, trojans, worms, etc. but is excellent for rogue applications.
SAS is also good at detecting malware but most of the time doesn't detect the latest rogueware.
To me, Hitman Pro is a joke. It only scans running processes not your complete system. So if you're infection with a worm or trojan, it doesn't detect it like other scanners. Also has high false positives and is NOT free.
Much better to use an online scanner like Symantec Security Check, F-Secure Online Virus Scanner, BitDefender Online Scanner, Trend Micro Housecall, Panda ActiveScan, etc. They offer free removal at no costs and will scan your complete system.
Thanks.