And later: Exasperated Shepard: "You are actually doing this right now."
Tali panicking after learning that EDI is an A.I.
Tevos reacting to X-COM making a military alliance with the geth. And then mediating a peace between the geth and the quarians.
She had to be hallucinating. That was the only explanation for this. The only other alternative, that the warmongering yahoos didn’t kill everything in their path, was unthinkable.
Shepard's pranks on EDI and Joker. He replaces her normal voice files with those of the guy who does all the movie trailer narrations (you know the voice). After Joker teases him about being caught with Tali sleeping on top of him after she was partway to a BSOD after Peak 15, Shepard casually super-glues Joker to his seat and places just out of his reach a gizmo that slowly sings out "10,000 Bottles of Beer on the Wall" with off-tune banjo accompaniment.
The rachni queen tries to shake hands with Shepard.
One of her tentacle arm things shot forward suddenly, and Shepard had to fight the instinctive urge to dive away from the motion. It proved to be the right choice a second later as the bulb on the end of it stopped just within his arm's reach. The bulb opened slightly and she trilled. "Friends?" she asked tentatively, the music in her voice full of hope.
When Sovereign reveals the truth about the Citadel and the mass relays.
Ashley: "Fucking called it!"
<Everyone stares at her.>
Ashley: "What? We did! We totally knew it was a trap!"
Shepard telling his new squad that they'll be outfitted with XCOM weaponry/gear, prompting an immediate nerdgasm from Garrus. When Shepard displays the Plasma Sniper Rifle, he notes that Garrus is staring at it with something like 'intense lust'.
The various occasions where the very people Shepard is coming to rescue faint in sheer terror at the sight/knowledge of "The Carnifex of Kar'Shann" coming for them, seemingly to inflict some horrible death on them. Shepard is a mixture of confused, exasperated, embarrassed, resigned when this happens.