Hello,

I recently read a blogpost about it there, and I wanted to improve that function, here it comes :

function Pin-Taskbar{
<# 
.SYNOPSIS This function pin a program to the Windows taskbar. 
.DESCRIPTION This function uses Shell.Application object. 
.PARAMETER Item Path to the object to pin. 
.EXAMPLE Pin-Taskbar -item C:WindowsSystem32mspaint.exe -Verbose 
.INPUTS 
.OUTPUTS 
.NOTES 
.LINK http://ItForDummies.net 
#>
[cmdletbinding()]
Param(
[Parameter(Mandatory =$true)]
[ValidateScript({Test-Path -Path $_ -PathType Leaf})]
[string]$Item
)
Write-Verbose -Message "Creating Shell.Application object..."
$Shell = New-Object -ComObject "Shell.Application"
$ItemParent = Split-Path -Path $Item -Parent
$ItemLeaf = Split-Path -Path $Item -Leaf
$Folder = $Shell.NameSpace($ItemParent)
$ItemObject = $Folder.ParseName($ItemLeaf)
$Verbs = $ItemObject.Verbs()
try{
Write-Verbose -Message "Trying to pin $ItemLeaf"
#$Verb = $Verbs | Where-Object -Property Name -EQ "Pin to Tas&kbar" -ErrorAction Stop #V3 only
$Verb = $Verbs | Where-Object {$_.Name -EQ "Pin to Tas&kbar"} -ErrorAction Stop
$Verb.DoIt()
}catch{Write-Error -Message "Unable to pin !"}
}
function Unpin-Taskbar{
<# 
.SYNOPSIS This function unpin a program of the Windows taskbar. 
.DESCRIPTION This function uses Shell.Application object. 
.PARAMETER Item Path to the object to unpin. 
.EXAMPLE unPin-Taskbar -item C:WindowsSystem32mspaint.exe -Verbose 
.INPUTS 
.OUTPUTS 
.NOTES 
.LINK http://ItForDummies.net 
#>
[cmdletbinding()]
Param(
[Parameter(Mandatory =$true)]
[ValidateScript({Test-Path -Path $_ -PathType Leaf})]
[string]$Item
)
Write-Verbose -Message "Creating Shell.Application object..."
$Shell = New-Object -ComObject "Shell.Application"
$ItemParent = Split-Path -Path $Item -Parent
$ItemLeaf = Split-Path -Path $Item -Leaf
$Folder = $Shell.NameSpace($ItemParent)
$ItemObject = $Folder.ParseName($ItemLeaf)
$Verbs = $ItemObject.Verbs()
try{
Write-Verbose -Message "Trying to unpin $ItemLeaf"
#$Verb = $Verbs | Where-Object -Property Name -EQ "Unpin from Tas&kbar" -ErrorAction Stop #V3 only
$Verb = $Verbs | Where-Object {$_.Name -EQ "Unpin from Tas&kbar"} -ErrorAction Stop
$Verb.DoIt()
}catch{Write-Error -Message "Unable to unpin !"}
}

You can paste it in a *.psm1 file to create a module, I recommend you to use the “#Requires -version 2” tag at the beginning of the file.
If you need help on how to use the functions, feel free to use :
Get-Help Pin-Taskbar -Full or Get-Help Unpin-Taskbar -Full.