>> See all items of Fate Series
(※This description covers both Fate/Zero and Fate/stay night.)
Gilgamesh is a solder known as the strongest savant.
He is arrogant and looks down on everyone else, but he also possesses the strength to justify his attitude. He first appears in Fate/stay night, and again in Fate/Zero, set ten years later, under a different name.
I can't go into much detail without including spoilers, but although the game is different, his personality is unchanged, so you can't miss him!
In fan comics, he appears sometimes with his master Kirei Kotomine, sometimes with his anime love interest Saber. He is often portrayed as a hard-partier, sometimes abusing (and sometimes abused by) Kirei.
He is famous on Japanese videos sites for his self-serving, pleasure-oriented nature.
As such, his motto is "The sorrows of others are the sweetest nectar," and his interactions with Kirei are often characterized in MAD by villainous laughter, while holding a wine glass in one hand!
「慢心せずして、何が王か!」