Golem building!
NWN and BG2 had some really interesting golem building quests, but I'd love to see more in depth artificer quests in upcoming RPGs, particularly Pillars and Torment. I really enjoyed the way Legend of Mana allowed you to design a golem sidekick and have it tag along (same for NWN). A golem sidekick like the one in Dragon Age is a nice start, but being able to play Dr. Frankenwizard and bringing your very own golem creation to life is much better.