Usually, a protagonist needs a voice and a character arc to be compelling, but Chell sidesteps these requirements. Chell, the main character of the "Portal" series, never says a word, but communicates a lot about herself through her actions and a few small environmental details; in fact, you won't even see her unless you position her in between two nearby portals. Chell is resolute. On her own and armed with nothing but a gun that shoots space-bending portals, Chell stands against not one, but two sociopathic AIs while working her way through twisted, mind-bending test chambers. She is more or less immune to psychological warfare (GLaDOS, one of Chell's computerized tormentors, digs into her with fat jokes almost constantly), and does not let simple things like pits of fire or being cryogenically frozen for centuries stop her from her single-minded quest to escape the testing facility.