1st ed
I can vaguely remember playing a beginner set of 1st ed, the Black Box with the big red blue eyed demon on the front. Would not mind seeing a few things brought back for nostalgia: rattlesnakes, spitting cobras pit vipers, whip snakes, rock pythons.
Sabre toothed cats, giant crocodiles, bronze golems, amber golems, thouls, rhagodessa.
Encumbrance in coins, letter tables for treasure, and so on.
And I kinda wish the Big Red Demon would make a reappearance: lookwise its much bigger than the modern pit fiend.