The simplest ideas are so often the best. And so often the most brutally challenging to play too - see Super Hexagon, for a recent masochistic example. Or free browser game No, Birdie, No!, which may just be the cruellest videogame I've ever played.
And is brilliant with it.
You play a dude hanging off a cliff by his fingertips. A cruel bird comes to the edge and looks down. And pecks and pecks and pecks and pecks at his desperate digits. They turn red and wounded, unable to grip. He falls. He dies. The end.
All you can do is delay that death by seconds.
A,S,D,F are your only controls, each one corresponding to matched pair of fingers - A for pinkies, F for index, others for the others. You need to keep as many buttons held down all the time as possible, or the suitably terrified-looking fellow will fall, but you need to rapidly release any endangered digits so that its brutal peck misses. This involves a sort of QWOP-esque co-ordination that I lack, but even the more adept will see success measured in seconds rather than minutes.
It succeeds both because its brutal and because, despite the Gobliiins-esque graphics, it does a fine, chilling job of conveying the terror and desperation of the awful, absurd situation.
Also it is funny when the little bird pecks the man's fingers.