Exodia the Forbidden One is a monster that's so hard to summon that nobody could figure it out (except Yugi). With it, Yugi beat Seto Kaiba in their first children's card game by claiming an automatic victory.
Exodia later appeared in "She Blinded Me With Card Games". After Steve the Martian summoned it, Exodia fired a laser beam at Joey (referencing the "Shoop Da Whoop", in which Exodia's face had Photoshopped onto it). The resulting blast had knocked Joey down, declaring him the loser of the Duel and leaving him to contemplate how a hologram that had no physical presence was able to cause physical injury to him.