Fate Stay Night 2006
This was my first foray into the Nasuverse.
Before playing the visual novel, watching and reading Fate Zero, watching Unlimited Blade Works, reading about Tsukihime, and theoretically watching the Tsukihime anime adaptation that doesn't actually exist, I watched Fate Stay Night 2006.
It was by no means a landmark series. In fact, it was rather mediocre.
However, in its mediocrity, it actually served as a great gateway show into anime in general.
It had an easy to follow storyline, generally likeable characters (Saber and Rin being standouts, Shirou being questionable).
I NORMALLY would recommend it to someone trying to get into anime.
And then Fate Stay Night Unlimited Blade Works 2014 came out and blew this show right out of the water. As far as adaptations go, the remake touched all of MAI WAIFU buttons, worked the shaft, and played with the sack for good measure.
Still, I do own a copy of F/SN 2006 because its what turned me into a Type-Lunatic.