Fullmetal Alchemist. I read the original manga but only watched the anime in bits and pieces. Watching the new one is still on my to-do list. I enjoy magic systems and the corresponding worldviews that obey their own internally consistent set of codified laws, which was epitomized by alchemy in FMA. It might just be that I've locked myself into this view from years of studying science, but I find magic without methodology and limitations to be a little uninteresting, like some kind of all-purpose plot sealant. It might even force us to
break our willing suspension of disbelief if things start getting out of hand and people start trying to magic themselves out of every bad situation. I once toyed with the idea of a setting in which each arcane spellcaster had his own theory concerning the nature of magic and even though none could reach any sort of consensus on even the the most basic underlying principles, every wizard nonetheless got positive results from spellcasting
within the context of his or her own worldview. Of course, this isn't appropriate for every setting. Sometimes, magic just needs to stay mysterious.