Mine was the titanite Catch Pole.
My first few runs were without the wiki or youtube because there is nothing I love more than a surprise. Therefore, I never learned to love the Drake Sword or Merchant's Katana like most people.
For me, landing a titanite Catch Pole just beneath Andre was the best day of my life. Compared to my +3 straight sword it would rip through enemies. Sadly, I almost never score one anymore and when I do I just stash it away because the spiked bat is my new go-to for low level play.
Runner up was Partizan.