What are the best magical systems in GURPS?

[ravenfish]

I'd just like to put in a word for the poor maligned core magic system. While some of the spells therein have faults (and I am led to understand that it tends to break down at very high point values), the core principal of individually learned spells which are usable basically at will but are exhausting to cast mimics very well much of the fantasy fiction I enjoy (really, Gandalf's recounting of his magic workings in Moria might have been taken straight from GURPS, and Raistlin Majere casts remarkably like a GURPS mage considering that he is supposed to be a DnD wizard), and it plays well enough at the table. It has all sorts of variant systems designed for it, so a setting can have many clearly different types of casters without the need to learn or create fundamentally different rulesets. Plus, it comes prebuilt. Most of the other systems either require huge amounts of assembly beforehand or else require far more judgement calls and outright haggling in play than I enjoy making as a GM or relying on as a player.