Get VMs that have an RDM (Raw device mapping)
Get-VM | Get-HardDisk | Where-Object {$_.DiskType -like "Raw*"} | Select @{N="VMName";E={$_.Parent}},Name,DiskType,@{N="LUN_ID";E={$_.ScsiCanonicalName}},@{N="VML_ID";E={$_.DeviceName}},Filename,CapacityGB