Two of three of the D Trilogy (he says he wants to play Enemy Zero at some point.)
Spy Fiction, an older and rather obscure game by the director of Deadly Premonition, wherein he does two playthroughs side-by-side (each in a rather different style) using both of the playable characters.
Ambiguous Gender: After one too many arguments in the chat over the gender of Casey during his The Deadalus Encounter stream, SGF claims that as a Featureless Protagonist Casey's gender is meant to be undefined and up to the player's choice. He's wrong, the manual refers to Casey as a man, as does Ari during his demonstration of the Non-Standard Game Over, which goes unnoticed by him but not by the chat.
Chewing the Scenery: In Episode 11 of Let's Play MODE, when he comes across a secret file containing the history of the Edom cult, he breaks his usual Deadpan Snarker demeanor and goes full ham, reading it in the most bombastic, over-the-top manner imaginable, complete with dramatic music. And it is glorious.
Deadpan Snarker: His modus operandi. When something actually makes him laugh, you know it's going to be a good one.
Early-Installment Weirdness: Many of his older LP videos didn't incorporate a mic, and instead used text below the action to explain his thoughts and make jokes. He brought it back for a bit with the D series of games, where it was done to preserve the first game's atmosphere (which he sometimes broke to explain how padded out the gameplay could be).
Foreshadowing: Accidentally creates a moment of this in his blind stream of 999, when he asks if Akane lives in the past.
Not So Stoic: He's usually quite good at keeping his cool, but sometimes slips into being annoyed (in D when Laura almost never catches on to the fact her dad's head is usually above her, a fact that causes him to briefly break atmosphere and tell her to "look up"), or breaks out in laughter (D2 had him laughing at a character treating Laura falling through the ceiling as normal.). He even almost let out an F-Bomb in his Deadly Premonition LP, where he failed one of the chase sequences (before cutting off to his next attempt.).
Changing the Shadow Gun's sound effect (due to finding the original noise incredibly annoying) during Shadow Man.
Shouting "Dumpster!" and jumping into one in Deadly Premonition.
This carries over to Spy Fiction.
"By the way, did I mention... Dumpster? Because dumpster."
Also from Deadly Premonition, giving people the human sternum instead of the proper quest item.
Saying "must be gettin' tired" in unison with the guards in Spy Fiction.
The Scare Cam with Dwayne "The Rock" Johnson's face. It's showed up in Slender, Slender's Woods, and White Noise.
Sarcasm Failure: Some of his dialogue on Shadows Of The Damned fails initially, either being interrupted or the characters Lampshading the ludicrousness of the world they inhabit, due to the fact that "the game just LPs itself".
Shown Their Work: His research into the subject of his games is pretty well done, bringing up the development history of some of the games.
Unusually Uninteresting Sight: During his playthrough of ILLBLEED, when going through the toy aisle of Killer Department Store, he passes a stack of what appears to be sex dolls without batting an eye. In a child's toy aisle.
In other weird games like [MODE] or Deadly Premonition, he tends to comment on weird things, but then roll right past them as if they don't matter without raising his voice.