Stoned Hannah, interrupting Selena and Jim's kiss by hitting Jim over the head with a bottle, believing he was biting Selena rather than kissing her.
Stoned Hannah emotionlessly telling one of the soldiers that all his comrades are probably dead, "and you'll be next." Made more hilarious by the fact that she ends up indirectly killing Major West.
The whole bit in the grocery store, particularly Frank eying the one section of apples that hasn't gone rotten and saying, "Mmmm...irradiated."
Jones fighting the infected in a frilly pink apron. Makes me giggle.
Jim encouraging Frank to let his daughter take a sleeping pill:
"Come on, let her live a little."
The soldiers trying to get the rage zombie off the roof of the car by driving in circles.
Jim's hilarious facial "DAMN!!!" facial expression when Selena leaves the room after kissing him.
When the cab drives away from the tunnel, one of the infected tries to chase it anyway for a while before slowing down and slouching. You can practically hear them thinking "Aw, man..." Maybe next time, buddy!
Jim jumping at the sound of a car alarm.
While the soldiers are defending the house from the infected:
Jones: "Mitch, I fucking got one!"
Mitchell: "What, you want a fucking sweetie? Keep shooting, you cunt!"
Considering the eerie silence of the scene up to that point, Jim belching as he leaves the hospital makes you smirk a little bit.
Jim smacking the first infected he sees (which happens to be a priest) in the face with a bag full of soda cans. And then freaking out and muttering "I should not have done that!" after realizing that he just smacked a priest in the face.