Who would it be? I would personally pick Wheatley from Portal 2. While kinda a screw-up, he's frickin hilarious.
Edit: Just to clarify, I meant like an artificial intelligence, a machine.
Edit: Cortana seems to be the favorite here (no surprise).
-
Obviously Ghost from Destiny... [spoiler]JK. Screw him.[/spoiler] [spoiler]Serena from Halo Wars.[/spoiler]