Well, maybe not the best, but certainly near the top... Cobblestone walls.
Why cobblestone wall? You ask.

Let me explain a little bit about them... They are small cobblestone walls that basically function as a fence; they have posts at all the corners, and they just all around look great.

These walls basically filled a void in my life. In all my builds, If I didn't want someone or something to go somewhere, you had two options. Stack 2 blocks high, or use the ugly fences. But these cobblestone walls look sexy, and work as fences.
If you do any medieval type building (castles or whatever), you know that this wall, with the posts at the end, would look great atop any castle wall.
My only wish was that these were in the game earlier.
Let me know what you think,
-Logan