Microsoft Security Essentials

mseinstall.exe /s /runwgacheck

You can also run mseinstall.exe /s /runwgacheck /o

The /o tells Security Essentials to NOT perform an auto update immediately following the deployment. 

The /runwgacheck option is needed or you will get error code -2147156188.

If you see error -2147156135 this means the installation file was built for a different architecture. e.g. Deploying the 32 bit installation to a 64 bit system will result in this error.

Also, error code 327424 may be returned which means that the install succeeded and a reboot is needed.  This can be added to the success codes to treat it as a successful deployment.