"Gar" is a term that was developed amongst English-speaking fans to refer to characters who are intensely masculine and/or macho. The term "gar" is generally credited to the image board 4chan, upon which someone reportedly attempted to say that they were "Gay for Archer" (as in Fate/Stay Night's Archer) but instead typed "Gar for Archer."
"Garfest" is an annual event on Fakku that takes place in the form of polls. It is the "manlier" summer alternative to the "Mote Mote" event. Garfest first starts off with users compiling a list of "gar" characters in a nomination thread. "gar" characters are pitted against each other in groups of 3, users vote for a winner and the victor moves on to the next round. Characters will climb the ladders until finally there is a single winner. Garfest is the invention of Fakku member TehMikuruSlave.