I was in the mood for some hack&slash action, so I went back to an old D2 melee sorc file in Act 4 Nightmare. A green Death Mask dropped on the River of Flame, which is pretty damned nice for a non-twinked melee character, especially at this point. I ID it, go to equip it and... "I can't use that".
What? *checks screen* Oh, level 66 requirement. Seriously Blizzard, who the hell thought L66 for Tal's Mask was a good idea when Death Masks start dropping in the middle of Nightmare? -_-
Aside from that, there were two instances when a randomly generated boss with crazy abilities insta-killed me from near-full health, but Diablo himself was completely trivial. Pretty typical D2 fare.