Get the serial number and service tags for ESXi hosts

Get-ESXiSerials.ps1

function Get-ESXiSerials {
<#
    .SYNOPSIS
    Get the serial number and service tags for ESXi hosts 
#>
    Param(
        # Full name of host or a regex
        [Parameter(Mandatory = $false)]
        [string]$HostSpec
    )
    Get-View -ViewType HostSystem -Property Name, Hardware.SystemInfo `
        -Filter @{ 'Name' = $(if ($HostSpec) { $HostSpec } else { '' }) } | 
    Sort-Object -Property Name | Select-Object Name, 
    @{
        Name       = 'Serials'; 
        Expression = { $_.Hardware.SystemInfo | Select-Object `
            @{
                Name       = 'AssetTag'; 
                Expression = { $_.OtherIdentifyingInfo[0].IdentifierValue } 
            },
            @{
                Name       = 'ServiceTag'; 
                Expression = { $_.OtherIdentifyingInfo[1].IdentifierValue } 
            },
            @{
                Name       = 'EnclosureSerialNumberTag'; 
                Expression = { $_.OtherIdentifyingInfo[2].IdentifierValue } 
            },
            @{
                Name       = 'SerialNumberTag'; 
                Expression = { $_.OtherIdentifyingInfo[3].IdentifierValue } 
            } 
        } 
    } | Select-Object Name -ExpandProperty Serials | Format-Table
}

Updated version available in my HelperFunctions module.