anti virus for Server 2012 r2

"I have never had an issue."
How do you know?

We use Symantec Endpoint Protection across our network and it's always worked well for us.

I also will never have a server without AV as viruses can spread within a network. So even if you don't browse on your server it is still venerable.
We use System Center Endpoint Protection.

You can use Microsoft's System Center 2012 R2 Configuration Manager.  It contains the EndPoint client virus protection that supports Windows 2012 R2. If you've got a MSDN membership it is the way to go.

Also look at reducing use of privileged user accounts, minimising access to shares to only those people that need it, and carrying out regular backups. To servers, these are essential so taking a layered approach to security is probably your next best bet.

Thanks all, Paul: never had a virus on a server.  I think I'm going to try those two, or three.

I'll chime in with a second vote for Eset, and if you running the ERA on the network, you can manage all installs on the network from there.