I'm always fascinated by the way that fantasy writers' interests influence their magic systems, even though it's utterly predictable:
- linguist: magic words / language
- translator: magic powered specifically by translation between languages
- programmer: magic that follows rigidly defined rules, and therefore has bugs and exploits
- botanist: magic is derived from plants and their products
- eugenicist: magic is in your blood
- hack: magic only works in ways that support the plot
- pervert: sex magic
- Adrian Tchaikovsky: bug magic