No ultra hard ones particularly come to mind, certainly not the sorts everyone else is saying. I've beaten MW2, Black Ops, Gears 2, Alan Wake and Arkham Asylum on the hardest difficulties but whilst some or more of them may class as tough, I would imagine there are many far harder ones.
That said, I did go to slightly extreme lengths on the Sega Ultimate Collection pack to finish Mean Bean Machine, albeit this did involve using a level select code and the old "save the game at any point you want" option the compelation gave you, so I wouldn't count this. None the less, I started the final level, wrote down all the pieces I would get in order then spent fifteen minutes on Excel planning each move meticulously to get the best possible results, and it still took three tries to get it to work. That'd be buggeringly difficult to complete the game properly though.
By the way, nice Captcha - Chinese characters. Think I might load another one there.