Like how Mario became the face of Nintendo and Sonic became the face of Sega, video game mascots can change the way people look at game studios. Recently they haven't been very popular with mainstream game studios but I've noticed several indie game developers have their own video game mascots. Has anyone else seen any recent, good examples of video game mascots? Do you think that they are important for defining a game studio's identity (or just marketing) anymore?

Maybe you could consider Master Chief a mascot for Bungie?

The common thing with all of the examples given (Mario, Sonic, and to a lesser extent Master Chief) is that they've been repeatedly used in many games; and except for Master Chief not just as the title character of their own games. Mario originated from an older game (having basically evolved from "jumping man" in Donkey Kong), featured in all of the Mario Brothers games, is in Mario Kart, Mario Party, and a number of other titles. Sonic appears in his own games, various sports titles, and others. Master Chief features in an entire series of Halo games.

A lot of modern characters are only used once, or might appear in one or two sequels at most.

Master Chief would be a mascot for Microsoft.

I'm not sure I'd call Keen a mascot, and certainly not the Companion Cube (which is just culturally significant - if Valve had a mascot, it was the Headcrab for a while).

I'm not claiming that they are adequate mascots, only that they are the least unsuitable candidates for the respective companies, and above average for the modern Western trends of AAA game development.

Imagining, say, a 6 years old girl buying a headband decorated with a Headcrab (counterexample) or Headcrab-shaped slippers (counterexample) is a little difficult: very few characters from macho games are loveable, developing an ambivalent attachment to familiar enemies like the Headcrab (or the imp from Doom etc.) is evidence that the game doesn't offer players anybody else to like.

Compared to the average game developer, both id and Valve are long-lived, highly regarded and makers of unusually great games; for most game studios, looking for a mascot would be outright silly. Consider Rockstar Games: their nicest characters are probably in Bully. Consider Infinity Ward, who published 7 Call of Duty games in about 10 years and nothing else. Consider Firaxis and Maxis: do they have any character at all between them? The list becomes quite depressing; exceptions like LucasArts only make everybody else look worse.