It is one of the more powerful melee type weapons as it has been known to slice the head off of opponents with a single slice and is not as heavy as the cumbersome chainsaw. It can also kill pedestrians by stabbing if cutting their heads off won't work. One note of interest is in 1998, Toni Cipriani and Kazuki Kasen engage in a duel on the roof of the Big Shot Casino with katanas (though the player may choose to use other weapons.) Snakehead and CJ engage in a similar duel, which, again, allows the player to simply pull out a firearm and finish the job quickly, but, it can be assumed that Toni and Carl would have defeated their opponents by sword in the game canon.
Hashbury, San Fierro - In the underground pedestrian tunnel behind the Hippy Shopper.
El Quebrados, Tierra Robada - Behind a small building in the trailer park in the north part of El Quebrados. From the El Quebrados Safehouse, head north and cross the street. Once you cross the street you should see a black, white, and blue trailer ahead of you. Go to the north end of this trailer and turn left. You should see a small building that does not look like a trailer. The Katana is at the north part of this small building.