The Nerd has been known to defecate on video games (and people) when frustrated. This is a list of all the shitting scenes in AVGN episodes.
Nightmare on Elm Street
When the Nerd and his clones are arguing on how they should destroy the "A Nightmare on Elm Street" NES cartridge, one of them suggests shitting on it, which the Nerd agrees. But since he doesn't have to take one, one of his clones shits on it for him. Before he finishes, he is killed by Freddy Krueger.
Bugs Bunny's Birthday Blowout
This is probably the most well known instance of the Nerd shitting on something. After being mercilessly beaten by the Nerd, Bugs Bunny falls on his back and is forced to withstand what appears to be a gallon of diarrhea from the Nerd through a fake ass.
During the Halloween review, the Nerd is interrupted by two kids trick-or-treating. The Nerd, frustrated by this inconvenience, grabs the childrens' bag of candy and holds it wide open under his ass as he takes a liquid shit into it. He also puts an Atari 2600 console and his copy of Halloween in the same bag.
This leads to the kids calling him "the poopy man" when he later goes over to babysit them. The Nerd also uses the same bag of shit to smack Michael Myers.
Atari Jaguar Part 2
The Nerd remarks the Jaguar CD (on top of the Jaguar) looks like a toilet. He later concludes the episode by saying "The end. I gotta take a shit.". The Nerd then opens the Jaguar CD, squats over it, and craps out large chunks of clustered shit. It apparently smells worse than his other shits as he visibly seems disgusted (holding his nose). It evens seems to drive Boo away. This is the only instance where someone shits out solid stool instead of diarrhea in a Nerd episode.
Other shitting scenes
The Wizard of Oz
After the Nerd tosses the SNES cartridge of The Wizard of Oz, the Cowardly Lion suddenly turns over on his head and shits out forces of diarrhea, which plasters the game onto the Nerd's ceiling.
Bugs Bunny's Crazy Castle
For revenge on the Nerd for his previous shit on Bugs's face, Bugs knocks him to the ground and unleashes a plethora of giant rabbit pellets onto the Nerd's face and shoulders.
Star Wars Games
At the very end of the episode, while the Nerd is naming a bunch of made-up Star Wars games, a digitalized buffalo can be seen walking by his house through the basement window. Seconds later, it turns around and violently blasts a diarrhea shit through the Nerd's window, breaking it and causing the blinds to jump. A shocked Nerd then starts screaming and cursing about the ordeal and complains about having to clean it up.
When Lloyd Kauffman realizes how horrible the game with his name on it is, he decides to shit on it. After informing the Nerd he had eaten baked beans, he takes the NES game out of the Nintoaster and tosses it on the floor. He pulls down his pants, and lets a messy stream of thick diarrhea pour all over the game cartridge. The Nerd, disgusted by the event, uncontrollably vomits all over the game while Lloyd continues to shit on it.
On the 10th day of Shitsmas, the Toxic Crusaders cartridge can be seen on the floor in the Nerd's basement, still covered in puke and shit (he apparently never bothered to clean it up).