I just found this game out called Defender of the Favicon by a Mathieu Henri way back 2008. Seems that it hasn't been updated since then.
Anyway, Defender of the Favicon makes use of the favicon canvas as the game screen. You see that little square area that is usually beside every website's name and usually contains a particular website's logo? That right there is the favicon area. And that right there would serve as your Defender of the Favicon game area.
Just head on to this website to know more and hopefully play Defender of the Favicon: http://www.p01.org/releases/DEFENDER_of_the_favicon/
I bet your eyes are hurting now. I mean, playing a game with a 16x16 screen size, who wouldn't?
'Till my next installment.