Cargo Ship: Soldier and his Shovel, taken to the furthest extreme possible when he has sex with it.
Complete Monster: RED Spy. Not only was he plotting the deaths of his own team, part of the plan including successfully talking Heavy into sacrificing himself for Medic's sake as well as later locking Pyro and Medic in a room with a horde of vicious zombies, but he actually suggested that Engineer helped him rape Sniper before he killed him.
Hilarious in Hindsight: This fanfic was written before the "Scream Fortress" update, which introduced several cosmetic items that make players look like zombies and the Harder Than Hard "Caliginous Caper" Mann Vs. Machine mission, which replaces the robots with armed zombies.
Heavy stuck in the fence has become a very recognizable image in a large part Team Fortress 2 fandom. There's a lot of Black Comedy fanart interpretations out there.
Moral Event Horizon: Spy crosses this when he agrees to RED and BLU's orders to slaughter his own teammates.
Narm: It's a bit inappropriately amusing when Medic says, “Nein, nein, nein, nein, nein…”the second time Heavy gets stuck in the fence? But you'll stop laughing pretty quickly...
It was pretty creepy when the Soldier's shovel started to talk to him...but it's just hilarious when the Soldier has sex with it. Firstly, the situation is so ridiculous that it barrels through squick and ends up Crossing the Line Twice, and secondly, how is it even possible to have sex with a shovel?!