Seeing Kong: Skull Island (which is very silly, but also totally fun and enjoyable and way better than the endless, overwrought Peter Jackson version) inspired me to take another look at Gary Gygax's AD&D module WG6: Isle of the Ape, which is, in simplest terms, an adventure about going to Skull Island, killing King Kong, and taking his stuff.
The adventure itself is pretty good - the island is a total green inferno, an environment so hostile that even high level characters are likely to be overwhelmed, especially since the magical environment of the island neutralizes a lot of the best magic (which I know is a complaint a lot of folks have had about the adventure over the years, but it's consistent with other high-level AD&D adventures and is actually consistent with the conceit in the latest movie that strange environmental effects preclude many technical advantages, like radio communication). The action is mostly combat and attrition, and in that regard it's pretty one-note, but there are at least a few opportunities for other aspects of play - some potential negotiations, and a couple of puzzles. When we played it back in the day we never finished it - we got bored by the relentless grindy combat and gave up on it - but I don't think it necessarily has to go down that way; a more careful approach could probably avoid a lot of the combat and make progress more quickly. This feels to me, on the basis of this recent re-reading, like an adventure that's worth playing, but if I were to do so (or recommend that others do so) I suggest a couple of changes:
1. The framing story is weak. Not just because it involves two full pages of excruciating read-aloud text, but for the whole notion that a group of super-powerful characters (this was the highest level AD&D module TSR had published up to that point) are being sent on an errand run to fetch a macguffin for some NPCs. That kind of thing is semi-acceptable for low level adventures (though even there I'm usually annoyed by it), but 18th level characters should be way, way beyond that. They're the ones who should be sending parties out on missions to fetch macguffins for them!
Luckily, this can be dropped without having to change anything else about the adventure. Just have the players learn the story on their own, and find their own means of getting there (I'm partial to actually venturing into the depths of Greyhawk Castle, but that would require a lot of extra prep work to set up), and go not to retrieve the Crook of Rao for offstage NPCs but to keep and use it themselves. The finale still works as-is - except that the players will want to avoid giving it up to either side, and the key to success will be sneaking out the back door with the loot while the two sides are ducking it out.
2. In all the movies, especially the most recent one, Kong is the hero! He's noble. We love seeing him smash stuff and are sad when he dies at the end. So making the premise of the adventure to kill him and take his stuff puts the players in the position of the bad guys - the ones we want to see get humiliated and smashed by Kong. That made sense in the original Greyhawk Castle version, when the players were all amoral and greedy and Skull Island was effectively a honeypot to lure overconfident characters to their doom, just like the Tomb of Horrors. But it doesn't work in the context of the module, where the players are supposedly good guys, and are killing Kong just because he's an incidental obstacle in the way of their goal, and especially because they're tough enough that, assuming they make it that far, they'll probably beat him in a fight.
I'd rather expand the scope so that it doesn't have to be about killing Kong. Maybe they can sneak past or distract him in order to steal his treasure without having to fight him. Maybe a PC can befriend him and convince him to give up the treasure willingly - maybe trading it for something. And best of all, maybe the PCs can team up with him against invading bad guys, directly or indirectly. The first two are compatible with the adventure as published, even though they aren't really discussed - you just need players who will think of it and a DM flexible enough to roll with it. The third requires some expansion - for the DM to create and send a rival adventuring party onto the island. It makes sense there would be one - given the premise of the adventure it's actually more surprising there isn't one. It raises the stakes and expands the scope and makes the adventure way more dynamic and interesting. Plus if the players are smart enough to team up with Kong against the rival party, it gives them the opportunity to cheer him on. Maybe there's even a way one of the players could take over Kong as their character for awhile via a Magic Jar or something. Now that would be a really awesome finale!