The character Gilgamesh is always depicted as an extremely tall and very muscular humanoid. He has several arms, and each one wields a different sword--usually these swords are some of Final Fantasy's most identifiable blades, such as the Excalibur, Masamune, and Buster Sword. A recurring joke is that sometimes Gilgy will pull a blade called the 'Excalipoor,' which will do little (if any) damage.
Gilgamesh has appeared several times throughout the Final Fantasy series. Most recently, he appeared as a bonus character in Dissidia 012: Final Fantasy. However, his first appearance was in the much-older Final Fantasy V. Let's take a look at Gilgy's appearances throughout Final Fantasy history...
Final Fantasy V-1992
This was Gilgamesh's first appearance, and was a recurring boss enemy. In-game, he was second in command to the game's primary antagonist, Ex Death. Gilgamesh established himself as a unique character through his hammy, over-the-top dialogue.
Suuuure ya did, Gilgy...
Final Fantasy VIII-1999
Gilgamesh's next chronological appearance was in 1998's Final Fantasy VIII. He didn't appear as an enemy, however. He appears as Guardian Force (this game's version of summons) that the player can't control--his appearances are randomized.
Final Fantasy IX-2000
Gilgamesh only kinda makes a half-appearance here. He appears as an NPC townsperson in Alexandria. His identity is only revealed much later in the game, however.
Final Fantasy XI-2004
In a completely different appearance, Gilgamesh appears as a regular human NPC. He a political leader of Norg, a city on Elshimo Island.
Final Fantasy XII-2006
In an appearance more akin to his original, Gilgamesh appears as a boss. In this incarnation, he is an elite mark found in the Lhusu Mines. He makes a return appearance for the game's sequel, Revenant Wings.
That Buster Sword sure looks funny...
Dissidia: Final Fantasy-2009
Gilgamesh makes a brief cameo in the original Dissidia as a Summonstone. If called, Gilgy will either triple your Bravery (referencing Excalibur), or reduce it to 1 (referencing Excalipoor).
Dissidia 012: Final Fantasy-2011
Dissidia's sequel features Gilgamesh much more prominently, almost as much as his original role. He is available as a bonus playable character, marking his first appearance in the series as a PC. He is aligned with Chaos, and retains his trademark goofiness (and resentment towards Final Fantasy V protagonist Bartz).
And the fandom rejoiced...
Other Appearances and Remakes
With so many remakes/updates to older Final Fantasy games, Gilgamesh has been retrofitted into several games. In the Dawn of Souls and 20th Anniversary reissues of the original Final Fantasy, Gilgamesh is thrown in as a bonus boss. In Final Fantasy 4's sequel, The After Years, he's another cameo boss. In the GBA edition of Final Fantasy VI, he's a new Esper.
Gilgamesh is just one of Final Fantasy's recurring, memorable characters. Although no other one is quite as humorous as Gilgy, there are plenty of others to keep him company. Let's hope Squeenix continues to give him those small but memorable cameos! :)
"Enough expository banter! Now we fight like men! And ladies! And ladies who dress like men! For Gilgamesh...it is morphing time!"