I've said it before and I'll say it again - FFVII's Battle Arena, where you challenge a successive set of enemies. The longer you last, the more handicaps will add up, but the greater the reward. It would be perfect for those who say the game is 'too easy' - 8 rounds in a 'Insanity' level Battle Arena facing down something like Ultima Weapon solo with a broken weapon and armour, levels cut down to 30, ilvl cut down to 50, HP halved, and transformed into a frog and/or chicken would very quickly make them change their tune.