How can I uninstall an application using PowerShell?

Question

$app = Get-WmiObject -Class Win32_Product | Where-Object { 
    $_.Name -match "Software Name" 
}

$app.Uninstall()

Edit: Rob found another way to do it with the Filter parameter:

$app = Get-WmiObject -Class Win32_Product `
                     -Filter "Name = 'Software Name'"

EDIT: Over the years this answer has gotten quite a few upvotes. I would like to add some comments. I have not used PowerShell since, but I remember observing some issues:

1. If there are more matches than 1 for the below script, it does not work and you must append the PowerShell filter that limits results to 1. I believe it's -First 1 but I'm not sure. Feel free to edit.
2. If the application is not installed by MSI it does not work. The reason it was written as below is because it modifies the MSI to uninstall without intervention, which is not always the default case when using the native uninstall string.

---

Using the WMI object takes forever. This is very fast if you just know the name of the program you want to uninstall.

$uninstall32 = gci "HKLM:\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall" | foreach { gp $_.PSPath } | ? { $_ -match "SOFTWARE NAME" } | select UninstallString
$uninstall64 = gci "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall" | foreach { gp $_.PSPath } | ? { $_ -match "SOFTWARE NAME" } | select UninstallString

if ($uninstall64) {
$uninstall64 = $uninstall64.UninstallString -Replace "msiexec.exe","" -Replace "/I","" -Replace "/X",""
$uninstall64 = $uninstall64.Trim()
Write "Uninstalling..."
start-process "msiexec.exe" -arg "/X $uninstall64 /qb" -Wait}
if ($uninstall32) {
$uninstall32 = $uninstall32.UninstallString -Replace "msiexec.exe","" -Replace "/I","" -Replace "/X",""
$uninstall32 = $uninstall32.Trim()
Write "Uninstalling..."
start-process "msiexec.exe" -arg "/X $uninstall32 /qb" -Wait}

To fix up the second method in Jeff Hillman's post, you could either do a:

$app = Get-WmiObject 
            -Query "SELECT * FROM Win32_Product WHERE Name = 'Software Name'"

Or

$app = Get-WmiObject -Class Win32_Product `
                     -Filter "Name = 'Software Name'"

One line of code:

get-package *notepad* |% { & $_.Meta.Attributes["UninstallString"]}