Morrowind. Poor combat, buggy as all hell, and ugly; but no game filled me with as much awe in its entirety as Morrowind did in the first half an hour.
Trigun. Sure, there are deeper anime out there, or ones that have better quality animation, but Trigun was the most fulfilling to watch.
Malazan Book of the Fallen. As a series, it is confusing as all fuck, and has some parts that have to be slogged through (I am looking at you, Toll the Hounds), but as far as series go, this one's scope, complexity, and detail put it just above A Song of Ice and Fire on my favorites' list.