Some of my favorite world-concepts are hard to tie to a specific origin. For example, I like shapeshifters who can take any form and have to consciously build themselves into the form they want to take, rather than shapeshifters who have some magical affinity with some type of animal. But other than Odo from ST Deep Space Nine, I can't recall any good examples of this type of shapeshifting.
I believe the Ender's Game series had something like this. Sometime in the Xenophobia line of the stories. Jane was able to transport and rebuild them instantaneously but had to keep their "soul" together as a construct of data in her mind.
Brandon Sanderson's Mistborn series has a magical system based on ingesting metals. Certain people are born with the ability to "burn" or metabolize one or more of these metals upon ingestion and tap into the magical properties locked within. The properties are paired, so that one metal allows a telekentic push while its pair allows a telekentic pull. One allows seeing the outcomes of different possible decisions in the past while its pair allows seeing into the future. And so on.
Sapkowski's The Witcher series (which was a series of entertaining books before it was turned into a video game series), has, in addition to more stereotypical elemental wizards, the witchers, who gain their powers through mutations resulting from intentional and potentially deadly exposure to chemicals/toxins. They also learn the mixing of potions and formation of elemental hand "signs" to aid them in combat. Witchers are trained professional monster slayers, but are typically not welcome in civilized society because of their mutations, which creates a source of conflict beyond the hero vs. monster one.
Robert Zelazny's Chronicles of Amber has a royal family in a fantasy realm who possesses the ability to select characteristics from the "shadow" between realities, mentally adding or subtracting these characteristics to create "shadows" of their own world essentially on the fly (Earth is one of these shadow worlds in the series). Learning this power involves traversing a maze called The Pattern. The family also has a deck of tarot cards that enables them to speak to each other across these worlds and even travel between them if both parties agree.
The movie Inception is set in our world but uses what could be viewed as a magic system based on the concept of "shared dreaming" and "dreams within dreams" with a number of specific rules about how these concepts operate.
