When I was a Windows user, of all the big anti-virus apps out there, the one that I got along with most was McAfee. It just seemed to do it's job with less fuss and intrusion than Norton or any of the other big ones.
McAffee VirusScan is even more stripped down and does a straightforward job. However, be warned that to uninstall it, you have to use the uninstaller that is bundled with the download or that can be downloaded from Softonic. If you simply drag and drop it to the trash, you'll be left with lots of annoying virus scan processes on your system that will cause all kinds of issues in the future.
If you get over the rather lengthy installation process, then McAfee VirusScan (formerly known as McAfee Virex) is a no fuss and quick virus checker. I've never had any virus problems on my Mac so far but a tool like this can never hurt. McAfee VirusScan isn't a real-time virus checker - rather it does one of scans of files you're worried about simply by dragging and dropping them into the interface. This is useful if you've received a file and are unsure whether it's safe to open.
Simply drag your file into the McAfee VirusScan and it will scan it instantly. For some reason, it seems to hide the results away in a little box underneath the drag and drop target but you can expand it by clicking the arrow. I'm sure if it does detect a virus, there is a much clearer warning of the result. There are very few configuration options but it does allow you to schedule automatic scans at specific times during the week which can target specific files. This is handy for targeting a download folder for example, or to prevent the need to scan your whole system.
McAfee VirusScan is updated regularly automatically and if you no need to check a virus definition, it takes you straight onto it's online database.
McAfee VirusScan is an effective tool for anyone that just wants to scan a one off file and doesn't need a real time scanner - just beware of the uninstallation process!