Get a Nokia 1100 - cheap (about $50, no contract or anything, for the 850/1900 model), B&W screen, wipe-clean keypad, small, light, long battery life, no camera or anything. Basically it's the old nokia stuff in a newer, smaller box.

I suspect it still has Snake on it, but you can't get a lot simpler than an 1100. The only other feature is a torch (ie, a white LED).

Hugo