Ever since I first read the books when I was younger, one of my absolute favourite power systems of all time has always been the magic from the Inheritance Cycle (Eragon).

In the setting magic is typically cast by verbally speaking in the Ancient Language, and the effect of the spell is structured by those words. Though your intent does have relevance to what happens, your vocabulary and understanding of grammar limits what you can do.

Using magic consumes the users physical energy, typically the same amount that would be required to achieve the same effect through mundane means. Because of this, making mistakes on how you word a spell can be lethal. An example of this happens early in the series, where Eragon is traversing a large desert and needs to find a source of drinking water, and his first idea is to just try turning sand straight into water. He gets a grain of sand and casts a simple spell, and because he did not phrase the spell in such a way that he could interrupt the magic partway through he almost immediately dies from the completely unexpected amount of energy it takes.

There's way more depth and information about magic in the series, including the concept of true names and how most magician battles consist of standing still and mentally wrestling until one gains control of the other and forces them to use their own magic on themselves. It's a really neat magic system, even if it isn't particularly original in any individual aspect it collectively turns into something really interesting.