Atari: ET if he counts as he's a iconic part of the American game crash way back in the '80s. Or Pac Man even though he was more famous in the arcade.

Nintendo : Link or Mario, or even Samus.

Sega : Sonic or the original mascot but usually forgotten about Alex the Kid.

Playstation: Lara Croft ? Crash Bandicoot ? Kratos ? Spyro ? Cloud ? Snake ?

Xbox : Master Chief.