$9.99 - Counter-Strike 1.6: http://store.steampowered.com/app/10/

$19.99 - Counter-Strike Source: http://store.steampowered.com/app/240/

$4.99 - Team Fortress Classic: http://store.steampowered.com/app/20/

$FREE - Team Fortress 2: http://store.steampowered.com/app/440/

$9.99 - Garry's Mod: http://store.steampowered.com/app/4000/

$19.99 - Sins of a Solar Empire: http://store.steampowered.com/app/201290/