Abridged Arena Array: While you can certainly find servers running other maps, there are quite a lot of 24/7 Island or 24/7 Arena servers out there.
Fan Nickname: Several. The "Badass Cutlass" for the Captain's primary weapon, due to it's high damage.
The Archer's Shortsword is the "Butterknife", while the Sharpshooter's Dagger is the "Letter Opener"
The Berserker's Sword/Axe combo is also commonly known as the "Lawnmower" or "Meat Grinder"
Game Breaker: Before version 2.3, the "Perfect Parry" could negate almost all damage from an attack, as well as leaving the opponent stunned and vulnerable to attack. To make matters worse, the two-handed weapons, in addition to dealing more damage, were also better at parrying than one-handed weapons. The Perfect Parry system was eventually toned down.
Memetic Mutation: Several of the placeholder voicelines present in the older versions of the game are subject to this, especially the Vikings:
"You are NO MAN!"
"Odin's Pizza Place!" Explanation "Odin bids us pace!"
"Ragnarök is a pony!" Explanation "Ragnarök is upon you!"