VirusBarrier Express from Intego is a free on-demand Mac antivirus. VirusBarrier Express scans for Mac malware only, so it's most suited for Mac only users. The lack of realtime on-access protection could be a plus or minus, depending on your needs. For example, VirusBarrier Express could be installed as a second antivirus scanner, or it could be used as part of a portable antivirus toolkit for support purposes. On the downside, on-demand only means the scanner won't prevent Mac virus infection - it will only detect and remove the malware after the fact.
If you need full-time protection or also want to scan for Windows viruses, VirusBarrier Express is too limited to do the job. However, if you're looking for a second opinion scanner or need a portable Mac antivirus scanner for support purposes, VirusBarrier Express could be an ideal fit.
Intego VirusBarrier Express is free and available for download from the Apple Mac App Store. English, Chinese, Dutch, French, German, Italian, Japanese, Portuguese, Russian, and Spanish language versions are available.