So, I've just finished the first book of the trilogy, and, because I'm a giant nerd for interesting magic systems, I've been looking up information on the various magical abilities in the Mistborn series. I think that Allomancy and Feruchemy are both neat, but the one that really captured my imagination is Hemalurgy.
I think that the idea of boiling down creatures into specific magical traits to pass along is an interesting and inherently flexible system. Can you make a spike that passes along a skill? You can certainly increase someone's abilities with it. After reading the wiki article about it, I immediately grabbed my copy of Greg Stolze's Reign off my shelf o' roleplaying goods and flipped to Dindavarian Death-Forging, which is much the same. Of course, in that system, the most accessible magic item is forged from an animal. After that, I flipped to the Infernal crafting system in exalted, where the items in question are powered by demons boiled down to their pure essence. In that case, not only are you typically playing evil characters, you're destroying demons, which is still not as bad as murdering people for magical potency.
The big problem in playing a Hemalurgist in a group setting would be justifying using (let alone making!) items that require the sacrifice of a living creature. As I haven't read the next two books in the series, I'm not sure how set in stone the Hemalurgy rules are, but if there is wiggle room, what kind of refluffing would be needed to soften the horror of it all? Especially if it can be carted off to be used in other settings; I think that the idea is too interesting to leave in the "villains only" box.