Crimson Echoes. In my opinion it's not really a very valuable entry, since it's fanmade, but hey, it is extremely difficult. The first maze and boss aren't that hellish, in fact it is pretty easy. But when you get to some bosses like the first fight with Kasmir, you get kind of annoyed. And then there are these bosses that... just can't be dealt with. Lebniz, per example, one of the most annoying bosses in the game, lives on the MOST ANNOYING GOD DAMN CHUNK OF EARTH IN THE GAME. If the Singing Mountain was actually PRESENT on every version of Chrono Trigger, i'd just flip off and never play the game again. Yes it's just that annoying.
Now for some games that have valuable entries. inFamous 2's Hard Mode is.. what the name says. Hard. The groups of enemies on top of buildings can kill you really really fast, the re-energization missions are frustratingly hard with 70+ enemies coming from ALL SIDES, and the ambushes are very frustrating.
For a different entry, i say Mardek 3. Of course, it's an online game, but has the length of a normal console game. Or not, i don't know. Anyways Mardek 3 begins with the very boring Sun Temple - Sandflow Caves(RRRRRGH) - Dark Palace level chain. Sun Temple is plain boring, Sandflow Caves is very long, and Dark Palace is just hard. Then there are the bosses of the game. None of the 3 in the levels i listed earlier are particularly hard, in fact, the other ones that come after them are. The booby trap bosses - the Bone Demon and the Security Demon are ridiculously hard, but they yield some good treasure. The Guardians are honestly easy - Water Guardian is a push-over, Fire Guardian is... complicated, and the Earth Guardian is just a plain lazy-ass thing. Save your rage for bosses like Qualna and the Annihilators. Save your laughs for the King of Goznor: God i love that bossfight.

Currently playing Pokémon Blaze Black/SoulSilver
Next up are Pokemon LeafGreen, VoltWhite 2, probably X, then either US or UM.