Dungeon Keeper 1 or Caesar 3 for PC.
Str8 Pimpin'
Lots of good ones here. My personal ones that I have suffered through (gladly) were; Super Ghosts n Ghouls, BattleToads, XCOM: Enemy Within, Contra: Shattered Soldier, Castle Shikigami 2, the original Prince of Persia, the whole Capcom WWII vertical shooter series, the Gradius series, The Adams Family: Fester's Quest. Even some levels in the Donkey Kong Country series could be tough. Freaking bramble scramble!
I'm sure there are others. As for the most difficult, that's hard. The first one that comes to mind is maybe on of the R-Type games? Those were brutal.
Honorable mention to the first Resident Evil remake on the Gamecube. The first game was pretty freaking hard, but when they added Crimson Heads........ugh.
Last edited by sharkythesharkdogg; 07-21-2014 at 06:24 PM.