"Okay, well that is problematic. We have to contend with someone else who's in here, possible threatening Nanako's life as we speak. There's no time to waste, let's hurry. *beat* (Gasp) Another gold shadow!"
Chewbacca Defence: He will often attribute things going wrong or unexpectedly to "science".
Cliffhanger: In his blind LPs of well-known games such as Final Fantasy VI, he coins the idea of a 'reverse cliffhanger' - when the audience mostly know what's going to happen next, but Jake himself doesn't.
Cool Sword: Owns one, as shown in one of JoshJepson 's vlogs. They use it to cut fruit. And then try to kill each other. Obviously.
Establishing Character Moment: An aversion; many viewers' first exposure to him was through the Battletoads race, in which the usually very even-tempered Jake is constantly raging and swearing at the game.
Flat "What.": Jake's default reaction to some of the wackier situations and characters in Ace Attorney.
Forgot About His Powers: In his P3 FES Let's Play, he complains that one of the Guardian bosses in Tartarus would be so much easier if he had access to a party healing spell. Several parts earlier he showed off Cadenza, a fusion spell that heals the whole party. Not once in his many attempts to defeat the boss does he remember this, which is most likely understandable considering the requirements may be more trouble than it's worth.
The Battletoads race may have brought the worst out of him.
Heroic RROD: In the sequence of events immediately following his below-mentioned Large Ham moment, his voice is pretty hoarse, something that he himself comments about.
Hilarity Ensues: Jake wanted a zombie-themed game to LP alongside Persona 3, so he went and picked up the only one that looked interesting to him for a blind LP. He picked Lollipop Chainsaw. His reaction to the intro video alone is enough to let everyone involved know what they're in for:
And when he started his Social Link with Kanji, he later calls Kanji "Kanju" instead due to a typo in the game.
Another one for Persona 4 Golden: Consistently not having enough courage(or rather, interior crocodile masculinity) to pick a dialogue option despite wanting to, with only a different stat popping up once or twice.
In episode 17 of New Super Mario Bros. 2, Jake dies, leaving Josh to take only one of two possible routes. "Well, let's hope there's not a coin th—" (star coin appears on other route)
During his battle with Nerapa in Final Fantasy VI, Jake declares that there's no way he's going to sit through the cutscene leading up to it again. Not a second later, Nerapa one-shots his last party member with Fire 3. Jake is so stunned that he just repeats "Fire 3?!" for a good twenty seconds.
Jake himself isn't received much better by the other players.
Verbal Tic: "Gladly", "Truly", "Nice!", "Sad.", etc.
He also says 'however' a lot to fill gaps between sentences.
Weapon of Choice: In his co-op Resident Evil 5 LP on Proton Jon's channel, Jake enjoys using the stun baton and will attempt to use it on an enemy at least once per part. Leads to Irony when he starts frequently encountering enemies who also have a stun baton and manage to get him with it.
SuperJeenius: Did he say 'insects'? Cuz I really hate bugs...
More specifically he really doesn't like spiders, which comes up in his Resident Evil 5 co-op with ProtonJon.
It's practically becoming a running gag in the RE 5 LP that whenever Jon starts to give warning about a new enemy type being introduced ("One of your favorite enemies from Resident Evil 4," "A traditional Resident Evil enemy," etc.), Jake pretty much always thinks it's spiders, even after they've already encountered them.