2. Ellen McLain (Portal)
Though Ellen McLain might not have the extensive CV that Jennifer Hale has, she ranks a little higher on this list because of the iconic niche she has carved out for herself, largely by playing as GLaDOS in Valve's Portal series, as well as the Combine Overwatch in Half-Life 2. It's the stingingly funny, witty scripts that combine with McLain's performance to bring her robotic character to life; the stifled, mechanised manner in which she speaks - assisted by some digital tinkering in post-production - helps to give McClain's character a creepy, sinister detachment as she belittles Chell throughout the game's mind-bending levels. Still, the best comes at the end of the games, as GLaDOS serenades us with a song through the credits, with "Still Alive" from the end of the first game being particularly acclaimed. McLain, an opera singer herself, actually sang the parts and received a huge amount of fanfare for her efforts, helping to make a fiendishly original and inventive game feel even more distinct in the world of rote first-person shooters.