Post an anime characters that uses a katana to fight .

Jin from Samurai Champloo.

Also, Zoro, from One Piece, uses three katanas.

Kenshin Himura (Rurouni Kenshin)
Yu Kanda (D. Gray-Man)
Setsuna (Negima!?)
Rukia and Ichigo (Bleach)
Sasuke and Itachi Uchiha (Naruto Shippuden)
Jubei (Ninja Scroll)
Inuyasha and Sesshomaru

rin from blue exorcist
kenshin from rurouni kenshin
kairi (character transformed) from shugo chara

Roronoa Zoro from one piece :3

Saeko Busujima (HOTD)

Toshiro from Bleach.

The members of Shinsengumi from Gintama