Some lists tell you "no" or "This list cannot be deleted." when you try to delete them. Sometimes it's just the allowdeletion flag.
$lname = "list name here"
$wname = "http://yoursite.whatever"
$web = Get-SPWeb $wname
$l = $web.Lists | where {$_.Title -eq $lname}
$l.AllowDeletion = $true
$l.Update()
$web.Lists.Delete($l.ID)

goodbye pesky list