Over at RPG Blog II, they ask the question: "What's Your Favorite Magic System?".
Since this blog is overwhelmingly focused on LBB-style OD&D, it probably will come as no surprise when I say "Hedge Magic".
It's true. I prefer vancian magic, although not with as many frills as post-0e versions of D&D. There's a certain appeal to Ars Magica-style verb+noun, and Fantasy Wargaming's astrological aspect-base magic is a guilty pleasure... but the one I think has the most appeal and usefulness without being either overpowered or too limited is S. John Ross's little hedge magic system. I also like a couple of the magic systems in GURPS Fantasy II (Madlands,) specifically soulless poetic magic and Savarginian themed magic, but perhaps they are too open-ended... unless maybe I combined them with hedge magic.
Now there's an idea...