One of the most famous spells from Dungeons and Dragons, found in every edition except for 4e, is the Wish spell. Basically, the way that spell works is that the player tells the DM the desired effect (usually in the form of a wish, like "I wish that..."), and the DM then interprets that wish and decides how to grant it. For obvious reasons, that won't work in a CRPG, at least not without some fancy natural language processing, and even then it can't be completely open.

So, of course, in a CRPG, the spell needs to be handled in a different manner. Here are some that I have seen:
* Wizardry 1-5: There are 7 possible effects. Typically, the game will randomly choose 3 of them, and the player chooses 1 of the 3. These effects are quire powerful, including things like teleporting the enemies or reviving all dead party members, but the spell will level drain the caster. (In some versions of Wizardry 1, you don't get any choice about the effect. In Wizardry 4, the spell exists, and it is properly implemented (at least in the Apple 2 version), but it will always fail because your level isn't high enough for it to work, and will never be high enough.)
* Baldur's Gate 2: Limited Wish allows you to choose from a list of effects depending on Wisdom (a stat arcane casters otherwise don't need). Wish (introduced in Throne of Bhaal) chooses 5 random effects, some good, some bad, with Wisdom again having an effect, and the player chooses one of them. (The only unusual cost for Wish is the possibility of having to choose between bad effects.)
* Nethack: When you get a wish, you type in the name of an item, and you get that item. There are limits; the game won't give you powerful enchantments, you won't always get artifacts that you wish for, and the game won't give you the real Amulet of Yendor (which is the item you're tasked to retrieve), but you still get to choose what item you want. (Note that this is unlike the previous examples.)

What other Wish implementations have you seen in CRPGs, and what are your favorite ways of handling this effect?

(Note that I count JRPGs as CRPGs, though the only examples of wishes in Japanese-made CRPGs are in games that are like Wizardry.)

Can't say I've seen in it any game I played (no, still didn't play BG2), but thinking that a reasonable implementation would be something like fate points in Arcanum or asking the Talisman for help in Lords of Xulima with the DLC installed, sort of a limited built-in cheat, with a list of options to choose from and difficult / time-consuming ways to gain the right to use. Any randomness just means frustration, and reloading until you get what you want.

In the cases I mention, reloading either isn't an option or isn't a particularly good option. Specifically:
* Wizardry: The early Wizardry games (1-3 and 5) have perma-death like mechanics, so you can't really reload if you don't see the effect you need. (With that said, you *can* avoid the XP loss by teleporting out of the battle.) Also, unless you're looking to revive characters, the effects tend to only be useful during battle.
* Baldur's Gate 2: Wish is largely a combat spell. Unless you're using it for healing, wish resting (using the spell to regain your magic), or to get 25 intelligence (for scribing spells), it's only going to be used during combat, and BG2 doesn't let you save if the game thinks you're in combat.
* Nethack has roguelike-style permadeath (after all, it *is* considered a roguelike), so you're not going to reload if you don't like the effects of a wish, unless you're using explore mode to experiment with the capabilities of wishes. (Also, wishes here don't work the way they do in the other two examples I gave.)

Interestingly enough, there are some Japanese developed Wizardry-likes (or DRPGs, if you prefer) that allow you to preview the available effects of a wish-like spell, and will allow you to cancel casting the spell if you don't see the effect you want. I've seen this in Elminage Gothic, Saviors of Sapphire Wings, and I think Wizardry: Labyrinth of Lost Souls does this as well. (Note: Stranger of Sword City does not; the Miracle divinity gives you no choice, instead randomly choosing 1 or 4 effects. Also, note that it can revive, but it is unable to restore LP.)

ADOM has a powerful Wish spell. You have to actually write down what you are wishing for, and beware of it...

I can't recall of any game that I've played that has a "Wish" system that wasn't directly related to debugging/wizard mode.

I haven't seen it done in CRPGs that I've played.

But the other effect (the "lesser effect") in the source material/D&D is that Wish can mimic any other spell or effect known, so an easy way to implement would be "cast wish, pop up menu of all other spells and abilities int he game, and code a special couple effects that appear only in this list, like the one that sets gold to max".

I haven't seen a good implementation of "wishes" in videogames either, but this has to be expected; when you play a pen and paper RPG you are playing with humans, while programs have a very limited capacity of interpretation. It would be impossible to give the player such an amoutn of freedom, since you can wish for literally anything.

The Magic of Scheherazade actually has a spell that does this, and in addition it maxes out every consumable item.

Even better, the spell is found in the first chapter.

Actually, all the Great Magic spells in that game feel like effects that one would expect from a spell like Wish, like making it rain in the desert, turning winter into spring, changing the main character's class (when there's no mosque nearby), and reviving and restoring everyone.

I wish to thank you for properly using CRPG.
I also wish more people knew that CRPG are all computer/console RPG's, and not just WRPG's.