A very sly one, when Link comments that the earth appears to have warmed up, stating that it is 'a convenient truth'.
We have another when Monger shows videos of the monsters at Area 52. After he says the name of one monster, the coffee lady screams in terror, every single time, to the point where Monger can't take it anymore and asks someone to get her the hell out. Then he finishes by introducing Ginormica, and we hear another female scream. It was the President.
The scene on the the spaceship where B.O.B., upon receiving a gun and pretending to be part of the invading army, accidentally activates the gun and kills a goon- it's not so much what B.O.B. does but the expression on his face when it happens- you can almost hear him thinking oh look a dead goon, COOOOOOOOOL...
The line leading up to that moment. The delivery is just so absolutely perfect.
Gallaxhar's recounting of his origin, and the destruction of his planet. As it's told while he's going through the cloning machine, it cuts him off every few seconds. And because he doesn't seem to realize this, we're treated to a few random details that are downright hilarious, starting with a horrible secret from his parents, encountering a giant (blank) after leaving home, shortly thereafter being married to someone, and then having marital trouble. By that point, he's decided that Susan knows too much, completely missing the look of utter confusion on her face.
Gallaxhar: And I was all "no way", and she was all "yes way", and I was all- *slam*
B.O.B.: No, no, your monster name! You know, when people see you coming down the street? "Oh, look out, there's—?" *looks expectantly at Susan*
Susan: *flatly* Susan.
B.O.B. *awkward pause* Suuuuuuusaaaaan! Ooh, I just scared myself!
"We need our top scientific minds on this. Get India on the phone."
During the fight with the giant robot, Susan's enormous size and strength makes her invaluable for engaging the robot, and protecting the innocent bystanders on the Golden Gate Bridge. The rest of the monsters just look on in awe, as she struggles to multitask fighting a large threat and saving lives.
Susan:[Struggles to fend off a giant robot hand, maintain her footing on the crumbling bridge, and keep bystanders from falling off]