I started watching Fate/Zero recently and it's awesome. I'm on season two now.
Black Butler/Kuroshitsuji. What can I say except that I'm four episodes in and yet have no understanding of the plot? The premise is cool (sort of), but the episodes thus far are iffy, ranging from haphazard slapdash humor to the stereotypical whiny characters who add nothing of interest. The only redeeming point is Sebastian, who is "a demon and a butler" in the most literal sense I can stress upon.