So at some point I had an idea for a different kind of magic/power system, and basically just wanted to scribble it down while I remembered. I'm certain that someone has already thought of this for an existing game; I just haven't come across it yet so I don't know where.
The immediate inspiration was reading some White Wolf stuff, which to my mind has a real problem with powers. Basically, they want you to have supernatural powers that sound really cool (and which, in game fiction, are really cool). Unfortunately, they also want to make those same powers very specific in their mechanical capabilities.
There are different possible interpretations of this. A generous reading is that, although White Wolf want to enthuse readers and fill their mind with possibilities, they're concerned that vague rules would leave the Storyteller to create mechanics each time a power was used; the narrow capabilities are designed to lighten the load for STs and avoid balance issues. A harsher reading is that White Wolf aren't very good at matching mechanics to fluff, and are violently averse to giving players access to tools that might derail the Storyteller's beautiful plot; giving them very very specific tools ensures the Storyteller knows exactly what their capabilities are and can overrule requests for a broader interpretation.
Given that utterly broken powers have been a mainstay of the White Wolf experience from its inception, through its history, to the present day, and many of the powers are so oddly-written that the Storyteller still has to make arbitrary rulings on what's allowed, I'm going to have to plump for the latter.
There are a couple of downsides to this mixture. One is that players can be confused and disappointed when (for example) the power that they think allows them to overwhelm enemies with raw terror can be used exclusively to make them run away from you. The other is that you have to pay attention to what's possible, and some things that seem equivalent may be impossible because the designer didn't think about it, and there may be odd gaps in your supernatural arsenal.
My idea is
basically the complete opposite of this ("complete opposite" is not a helpful description, and probably straight-up wrong) a very different approach to this.
So the White Wolf tack can basically be seen as permissive mechanics: You Can Do This. I've seen (somewhere) a more quantitative mechanics: You Can Do X Amount of This. I've seen narrative-quantitative approaches: You Can Roll Dice and Fluff the Result as This.
Insofar as I can classify it at all, I think this approach is more like narrative-dramatic. Essentially it's based on You Can Overcome These Challenges. Powers don't have any mechanical specifics at all; you simply choose a type of thing you can do, and decide how useful that ability is. Does it occasionally save you from mild inconvenience, or regularly allow you to achieve goals that would otherwise be beyond you?
- Trivial. The magic is nominal, or cosmetic, and of virtually no practical use (although it may be cool). Maybe you can change the colour of small items, create tiny illusions in your palm, create sparks,
- Convenient. The magic allows you to achieve something you could have done anyway, but sometimes saves you effort or time. For example, copying a document, flipping a light switch from a few feet away, reheating meals, making noises, cleaning objects, or giving someone an electric jolt instead of a pinch.
- Useful. The magic is a significant and regular asset that makes your life easier. For example, keeping your devices powered without charging (or even without batteries), locating an object you want within a room, protecting you from mild injury, telekinetically preparing meals while you watch TV, helping you win on the races, distracting an annoying person, providing a weapon, opening doors without the key, getting favours, or completing a task much faster than normal.
- Impressive. The magic provides major benefits or allows you to overcome substantial problems. For example, summoning a lost item, surviving dangerous situations, finding a person, learning hidden truths, getting into a secure area, providing a potent weapon, travelling great distances quickly, speaking new languages, removing physical barriers, or altering a person's opinion.
Note that the scale of your ability is absolute, even if you use it in different circumstances. If you have Convenient Electrokinesis and use it to turn on lights with your mind and therefore look cool, you cannot use this to turn off the forcefield using the switch on the other side of your prison barrier. Why? because that would be Impressive. It's up to you and the GM to establish why it isn't possible, if you care. In this case, clearly the barrier interferes with your mental powers.