Use the below if needing to target each Web or List in a Site Collection

$Site = Get-SPSite http://SiteCollection/
$Webs = $Site.AllWebs
foreach($Web in $Webs)
{
    #Code for each Web.

    ### Target Each List in current web
    $Weblists = $Web.Lists
    for ($i = 0; $i -lt $WebLists.Count; $i++)
    {
        $list = $web.Lists[$i]
        #Code for each list.
    }
    ### End of lists
}
$site.dispose()
$web.dispose()
$webs.dispose()