Giganto L is Kalin Kessler's Duel Runner. Its name is not mentioned in the anime, but is in Yu-Gi-Oh! 5D's World Championship 2010: Reverse of Arcadia.
In Yu-Gi-Oh! 5D's World Championship 2010: Reverse of Arcadia, the player can purchase the Giganto L frame from Chihiro for 40 Star Chips after Story Mode has been completed.