Even though we all know that new malware is being introduced every day, it's important to remember that all the old examples may still be a threat too. The only difference is that those old techniques and methods are continually refined to incorporate the sophistication of modern malware.
Just as early viruses were spread via infected floppy disks (remember those?), a common distribution method for today's malware is the ubiquitous USB thumb drive. The infamous Stuxnet worm has infected many computers that weren't even connected to the Internet, using the lowly thumb drive.