Mario's Cool Tiny Face 64:
It is a black screen. In the centre, there's a red pixel. That's it.
Mario's Cool Tiny Face 2: Bowser's revenge for N64 is coming...
(SCREENSHOT: Black screen, red pixel in the centre, a green pixel at its right)
I don't think there could be a game worst that Mario's Cool Tiny Face 64 (1). But, still, there's a game wich is worst than Mario's Cool Tiny Face 2: Bowser's revenge, and that game is, actually, Mario's Cool Tiny Face 64 (1).