See definition for 'sewer rat'. "Someone that orders Fireball Shooters at a gas station". This person would also rob the gas station at gunpoint with or without a nerf gun painted black-tip.
JR: I'm drinking Fireball shooters.
Ruairi: Youre a gas station shooter.
JR: How?
Ruairi: You bought fireball at a gas station register?
K.I.A.T. An acronym for Know It All Twat. They often remind you immediately and frequently that what you are doing is wrong. They go so far as to not only know what is right but will tell you what is right via any confrontation method(i.e. in-person, online in the DMs, passive aggressively, etc). They will suck the life out of any person they come into contact with because their ego feeds on everyone else's opinion about the knowledge they contain and bring forth to the group.
Tim: "You just need to 360 no scope superbounce into a 970 180 pipeturn, no biggie"
Kyle: We get it! You know how to play this game. You're such a KIAT, I'm done playing this bulls*** game.