Duel Computer

The KC DuelTek 1000 is a computer used by Seto Kaiba to practice dueling against. It appears in the anime when Kaiba tests his new, Battle City deck. Giving the computer his old deck, he defeats it using Obelisk the Tormentor.

Yu-Gi-Oh! World Championship Tournament 2004
The Duel Computer is an unlockable opponent in Yu-Gi-Oh! World Championship Tournament 2004.

If the player defeats all the level 5 duelists 15 times, and then deafeats Seto Kaiba 3 times in a row, the fourth time, they can duel the Duel Computer.

Yu-Gi-Oh! The Sacred Cards & Yu-Gi-Oh! Reshef of Destruction
The Duel Computer is an optional opponent in these two games.

It can be found it in KaibaCorp, and can choose the level of difficulty for the Duel. Its best card is F.G.D..

Deck
In the anime, It used many of Kaiba's Duelist Kingdom cards, including his "Blue-Eyes White Dragons".