Test a few out as some are MUCH better at keeping up with current threats than others.
Download a few "cracks" for programs (easy enough to find from google) that are usually in a zip or exe file (don't open/run them tho).
Go to
http://www.virustotal.com/ and upload the file and see who finds what. You'd be surprised at some of the bigger names in virus protection that don't pick up on trojans embedded in them.