I haven't played it yet myself, but I read that Outward doesn't have a level system at all. Instead, a character gains power through getting better gear and paying trainers to learn skills.

SaGa 2 has the stats/abilities of robots being solely defined by gear; it makes things interesting by not having specific body slots. Characters can equip multiple weapons without issue (you just have to choose which one to attack with each round), and robots have the unusual characteristic of being able to ignore body slots for armor (so they can equip multiple suits of armor at once). SaGa Frontier handles robots the same way, with the addition of being able to learn programs from enemy robots.

There's also monsters in early SaGa games, which change form on eating meat, getting all the abilities of the new form and losing those of the old form.

I could also imagine a game where your characters don't level up, but you instead recruit new, better, characters as the game goes on. Destiny of an Emperor is almost like that (you do get XP and levels, which give you access to better techniques, and a small number of characters do get stronger, but not most of them), and there's also early Shin Megami Tensei games (human characters level up, but monsters do not and have to be replaced with stronger ones; Nocturne lets monsters level up, but you're still better off upgrading to more powerful monsters).

I could also mention games like Zelda and Metroid, where the way to get power is to explore and find permanent upgrades scattered throughout the game world.

(If you'll notice, all of these games are Japanese, and all the RPGs are JRPGs or SaGa-likes; I am not as familiar with WRPGs, hence why I'm asking this question.)

Zwei?

Gothic 2 maybe.

Ryan mentioned Deus Ex 1. You find canisters that go in certain body slots, and you permanently choose one of two options. Like your foot slot can give you jumping or silent move. A cloaking canister can give you invis against people or invis against machines. You still gain xp though and spend it on skills (no levels)

KOTOR 1 has an alignment system. All jedi powers are good, neutral or evil, and as your alignment moves to an extreme, powers from the same alignment cost less while those from the opposite cost more. You still gain xp for levelling.

VTMB is perhaps my favorite game of all time. There are no levels as your hit point and blood pool are set for the game. You get xp, but it's NOT from combat. Rather, it's for doing tasks, giving a little leeway as to how you want to do those tasks. In a few cases you can get more xp for having the right skills and choosing the right dialog options. The vanilla game lets you train skills from books, but some mods replace the books with an email college option, which I think is cool. Another mod lets you diablerize certain vampires, giving you some of their power, power you could not gain otherwise.

As for your power being defined by gear, I'd think that falls more in the FPS or even stealth genres, something I know little about.

Akalabeth: World of Doom has a strange growth system. You increase your health by killing monsters in dungeons and then leaving the dungeon and the other stats increase by visiting Lord British the first time and completing quests.

Don't forget the permanent stat changes from using the amulet to transform.

Given that the game's RNG only advances when the player performs actions, and that the player can control the RNG seed (that's what the "lucky number" you enter is for), it's not that hard to exploit this to make the game really easy.

Ultima 1 is pretty similar to Akalabeth when it comes to its growth system, albeit with no transformation, and with signs that boost stats when checked. It's an interesting system, and this sort of thing is why I consider what I call "proto-RPGs" worth looking into. ("Proto-RPG" is the term I use to refer to RPGs that are so old that the genre's conventions haven't been firmly established; other games that could qualify include Wizardry (which feels a bit more conventional, but still has permadeath mechanics) and the original Dragon Quest (which is actually quite different, in interesting ways, from the rest of the series).)

Ultima IX has a similar system, as I recall: as one progresses the main plot, one cleanses shrines. Each time a shrine is cleansed, it offers a boost, primarily to the character's stats. There is no XP, and no level-system; just stats that are boosted. (Well, and gear to find.)

That said, I also recall that the choice of stat to boost determines the order in which one will get the boost, rather than a final build, as there are more shrines than stat boosts available. Thus one ends up with full stats, and the final shrines giving something else, if I do recall correectly. (Karma, perhaps? I forget. ^^; )

I could see a system that might boil down to something like this:

1) Do X
2) Earn a choice of Zs

Where "Z"s are boosts of some sort.

Bonus points if the "Z"s aren't numerical improvements, but new skills; thus the player doesn't become more inherently powerful, but instead possessed of a broader and thus more flexible range of skills.

Alas, I don't have an example of quite this to mind.

However, it does remind me of an option: Prey. (The new one.)

It's not exactly what I suggest above; one still collects "Y"s to be spent. However, it does feel a little different:

In Prey, the player finds (or is given, or manufactures) devices that can apply skills to their character. With these they can choose from an upgrade menu of various abilities; I think that some of the abilities are passive, but do recall that at least some are active skills.

Now, the devices are, essentially, obfuscated XP-points. However, they at least are rewarded a little differently, as some have to be actively found, and some can be made at a cost of crafting materials. Furthermore, I seem to recall that many of the upgrades are skills, rather than being all just stat upgrades.

So not a perfect option, but perhaps worth mentioning.

It's not an RPG (though many would say "open world with RPG elements"), but the PS4-exclusive Spider Man game gates your unlocking of new things (gadgets, suit papers, passive abilities) with tokens you earn by doing specific things. The game has crime tokens you earn by stopping crime, base tokens you earn by taking out enemy bases, research tokens you get by doing puzzles, etc. Each unlock uses some mix of those tokens to get. Certain ones are kept for later parts of the game, like you can't get your first research tokens until X point in the plot.

In the Heroes of Might and Magic games (the early ones at least), when you level up, you get a random stat along with your choice of two "feats".

Now that you mention it, Ultima Underworld does something similar: I think that one does accumulate XP, but on levelling one goes to a shrine and gets a stat upgrade randomly chosen from the stats governed by the shrine, if I recall correctly.

Ignoring the fact that it is still a level/xp system (and assuming you're correct about the random stat growth):

This approach has the issue in that it heavily encourages reloading. When the stat gained is random, a player has an incentive to reload until they get the desired stat increase.

Ultima 6 did this better, with the stat growth being deterministic (but was still a level/xp system).

(Ultima 5 had a problem with this, which is compounded by the fact that even getting the level up when you have enough XP requires resting and hoping that Lord British decides to appear, which requires good RNG.)

Yup; I never said that it was good (I really dislike it), only that I was reminded of it; and it is an unusual approach (in my own experience, at least).

That said, since this is a recommendation thread I should perhaps have thought to mention that I wasn't advocating for it--so my apologies! ^^;

I haven't played Ultima 5 or 6; from what you say, I doubt that I'd much like the progression systems in either. :/

On a general note, there seems to have been a surge in deck-building games, in which one progresses by selecting cards (essentially abilities) for a deck. (These may sometimes also have XP and levelling as a supporting form of progression.) Thus one's progression is in part determined by the cards presented at each offering, and in part by the player's selection from amongst those offered cards.

Many of these seem to take the Roguelike route: death costs the player all progression, and a new start comes with new cards and likely new encounters. However, I think that there may be some RPG-ish titles too, although I don't have specific recommendations offhand.