There’s been plenty of Unix viruses in the world. No OS can ever be 100% secure from viruses, unless you made it so the user couldn’t do anything. Computers are just like buildings, any door that can be opened for legitimate means can be opened for illegitimate means, if the OS will let a user install and run software it will let them install and run malware. The only real question is how many secret processes an OS will let run, that’s really the danger point in Windows, there’s way too many times a Windows machine is running code from god knows where without the user having any idea or buy in.
If by "plenty" you mean, "less than a hundred, most of which are theoretical," then sure.
If by "plenty" you mean "almost as many as the thousands of viruses for Windows, currently infecting at least 10% of all Windows machines," then no.
No OS can ever be 100% secure from viruses, unless you made it so the user couldn’t do anything.
This is a pointless argument. No on is saying that Windows should be 100% secure or that any other OS is 100% secure. But to continue to give Microsoft a pass for having the thousands of security issues it has had that allow these problems is just silly.
It's not impossible to build an OS that is resistant to malware. Apple does it, Sun does it, IBM does it. Microsoft needs to do it too.