BSG

 is a gun that slowly charges up to fire a large green projectile that, upon reaching its maximum distance, will detonate and severely damage all enemies in the room. The projectile itself will also deal impact damage, pierce enemies, and bounce off a wall once before detonating. However, if the projectile bounces off a wall more than once, it will dissipate without detonating.

Synergies

 * If the player has Big Shotgun, it fires five projectiles instead of three.
 * If the player has Thunderclap or Strafe Gun, shot speed is increased by 25% and the player's movement speed is slightly increased.

Trivia

 * With more than double the charge time of the Molotov Launcher, the Big Shooty gun has the slowest fire rate of all guns in the game.
 * This gun is a reference to a weapon called the BFG 9000 from the DOOM series.
 * The In The Mood synergy likely references the high walking speed of the character from Doom. The Thunderclap resembles another gun from Doom, whereas the STRAFE gun may refer to how fast the Doom Marine can strafe.
 * Similarly to how BSG stands for Big Shooty Gun, BFG stands for Big F*cking Gun.