Everything after 1e. Combat should be fast, fluid, and lethal, but the higher the edition, the slower and clunkier it gets. I'm just going to use a different system, because 1e books are mostly scans.
I think 2nd edition was the first time I'd ever been disappointed in a new edition of a game I had previously enjoyed. I cannot remember exactly what it was about 2nd edition I didn't like because it's been so long. The last time I ran a campaign it was for 4th edition, which had some problems, the Tsuruchi Bounty Hunter school was completely bonkers when it came to archery, but it worked fairly well. The latest edition switched to a system that uses proprietary dice like Fantasy Flight Games' Star Wars. Not my cup of tea.
So the question is begged "do people want to replicate Conan's adventures" or "the adventures of people who aren't main characters in Conan's world"? Because one will feel a lot more like D&D, and the other more like Runequest or Rolemaster.
We kind of run into some problems with interpreting the rules as written and rules as intended. Conan wouldn't just leap from a 200 foot chasm without something to slow his fall because Howard knew the audience wouldn't accept it. They'll accept a giant snake, gorilla monsters, and magic, but suspension of disbelief only goes so far. The player of a high enough level D&D character might just leap from that same chasm for lulz knowing he can't take enough damage to die.
Of course the rules are not a perfect representation of what the game world is. Players are very creative, and there simply aren't enough rules to cover every plan they come up with or action they execute. I remember years ago a letter to Palladium about what to do in the event a player character does something that would normally be monumentally suicidal. In the example, a player character jumped on a grenade, arguing it couldn't do enough damage to get through his SDC. (Characters in Palladium games have SDC and then Hit Points....I don't want to go too in-depth, but you usually took damage to SDC and had many more of that than you did Hit Points.)
Whoever wrote back from Palladium said to let the character die. The game in question wasn't Rifts, Hero's Unlimited, or one of their other more fantastical games where throwing yourself on a grenade was less likely to result in death, it was one of their more down to earth games. The person answering Palladium's fan mail basically said if a PC does something suicidal then just let them die no matter the rules as written. Personally, my advice would be to have the grenade to Hit Point damage directly, bypassing SDC altogether, but I can't say just killing the character is bad.