One of these days, the Academy Awards are going to be forced to recognize the talents of actors who appear on-screen as a CGI character. Many have thrown Andy Serkis' name around as the first person likely to break that barrier -- and it's no mystery why!
Serkis is the man who helped bring Gollum to life in the Lord of the Rings trilogy (as well as Caesar in Rise of the Planet of the Apes.) This was the first time an actor's performance was combined with digital animation to make this advanced of a CGI character live on the screen. Serkis was actually only supposed to voice Gollum, but when animators saw the way his face moved when recording dialogue, they knew they were onto something special.
Wearing a motion-capture suit, Serkis would eventually appear on camera opposite the real-life actors, and then the Gollum character would be placed over him in post-production. Director Peter Jackson relied on Star Wars legend George Lucas and producer Rick McCallum to help hone in on these concepts, and really became a trailblazer for a new style of filmmaking as a result.