After thinking about this for a second I'm going to go with
Fate/Stay Night.
Here's a funny story: When I started watching anime again after a few year absence in high school, I thought it would be an anime about a supernatural thriller mystery taking place at some creepy hotel. Hence the "Stay/Night" as to me it felt like "Stay the Night" at some place. Pretty misleading and weird to me at the time.
Loved the show to no end though, but Fate/Zero sounds more cooler than the latter.