In First and Only, Gaunt discusses with Rawne the defense of their barracks from rival regiment by the means of training shock-poles, using a random trooper right next to him as demonstration.
Shortly after Feygor gets an augmentic voice box that makes everything he says sound sarcastic, someone suggests that from now on he should raise a hand to let people know whenever he's actually being sarcastic. Feygor's reponse: "Oh, that's a good idea." Beat *Raises his hand*
In His Last Command, Ezrah doesn't get why Ayatani Zweil is bugging him... so he looks at Gaunt and asks if he can kill the man.
Rawne: "That probably sounded better in your head, didn't it?"
Wilder: "Yes. Really, much, much better."
When the events of Blood Pact cause Gaunt to make an unscheduled and incognito visit to the museum of the fallen Tower of the Plutocrat on Balhaut, he finds there are several chapels dedicated to the heroes that died taking it. His reaction on finding on dedicated to Commissar Ibram Gaunt of the Hyrkan 8th is priceless, and all the more funny that neither he nor his party can correct the mistake...
Meryn's beatdown in the medical clinic in Salvation's Reach after he proves to be too cowardly to shoot the assassin holding Yoncy hostage. Tona Criid goes after him first, only to get pulled off him by Gol Kolea and Major Rawne. Meryn starts demanding that Cridd be put up on charges while calling Captain Daur's fiance Elodie a "bitch" for apparently reporting his cowardice. Kolea pulls Cridd all the way off Meryn, and then tells him that he only did it so she'd be out of the way, and then decks Meryn with a punch of his own. Commissar Hark walks into the clinic and demands to know what happened, and while Meryn is demanding Kolea and Cridd be put up on charges, everyone present admits they have no idea what happened and saw nothing. Hark gets ready to dismiss the entire thing, when Ban Daur rolls up and punches Meryn in the face for calling Elodie a bitch, then says that they're done.
When Beltayn kills a Gereon occupation officer as he steps inside a shed while searching a farmstead where some of the Ghosts are hiding out.
In Blood Pact, Mabbon (a defector from the main Chaos force the Ghosts have been fighting for years now) and Gaunt have this exchange when the latter is helping the former keep running from both Blood Pact and the Inquisition after an old wound reopens.
Gaunt: Not far now, magir.
Mabbon: You're a good man, Gaunt.
Gaunt: If they take us, please don't say that to anyone. Tell them I'm your sworn enemy.
"Sabbat Martyr" Curth telling Gaunt she'll only do him a favor because he's so good in bed. In front of the whole regiment.
It backfires on her though as the regiment stares at her as if she's serious, making her retort that it was a joke irritatedly. Though that reaction alone is also hilarious, as everyone in earshot (which, as they're getting off their landers, is most of the regiment) immediately believes it. A few slack jaws and a couple dropped kitbags are mentioned.
The joke goes sideways later on when Curth reveals to Gaunt in Salvation's Reach she'd been pining over him for years.
Rawne's remark about his commander, mentioned in Necropolis: