Darvo: "I'm detecting a large security force heading your way. It's the Gri- No wait, it's the Corpus. Definitely the Corpus."
This is a Take That, Us referring to how the Lotus would always say additional forces were Grineer... when they were Corpus or Infested.
Darvo and his father arguing over family business while you are occupied tearing appart Corpus guards and fighting a Hyena pack.
Occasionally the AI of an enemy will be confused between two positions they can take cover in and the player's distance. This results in them running in circles endlessly.
Using Valkyr's Rip Line ability on a Scorpion finally giving them a taste of their own medicine.
The event where the Tenno rescue Darvo from his father, Frohd Bek. Throughout the entire mission, the two bicker about duty and freedom as the Tenno slaughter their way through Corpus troops, and Darvo keeps apologizing to the Tenno for having to listen to all this.
As intimidating Hek's interruption during the developer livestream was. His comment about throwing "Your beloved Lotus into the sun." is so narm inducing it becomes hillarious.
A good chunk of the alerts DE posts in the chat to tell players updates or hotfixes are coming (lovingly referred to as "redtext" by fans because of their red color) are filled with hilarity.
In the revamped Tutorial, when the Tenno realizes that Darvo's blueprint for the antidote for the parasite that is slowly turning the Tenno into Vor's puppet requires components that Darvo "conveniently" forgot to give them, Ordis has some... choice words for him. We don't actually hear the rant, but Darvo's response says it all.
Darvo: My mother may not be a gymnast, but she would never eat stuff like that!
Ordis's reaction to finding out the Tenno plans to raise a Kubrow on the ship.
Ordis: To think it's been years since a Kubrow SPREAD FILTH ALL— graced this ship! Operator, drop the egg into the system to begin breeding— DROP IT ON THE FLOOR.
Ordis has many moments when his voice switches abrubtly that can range from funny to slightly disturbing.