Tallahassee raging about the Hostess truck being filled with snowballs, when the viewer can see what looks like a blurry crate of Twinkies by the door, just out of sight.
Columbus trying to ride off on a motorcycle to save Little Rock and Wichita like a heroic Badass... and failing.
"Thank God for rednecks!" After finding a very hillbilly house with an H3 Hummer. With a case of weapons in the back.
"I'm in Garland, Texas. And it may look like zombies destroyed it, but that's actually just Garland."
The zombie three-legged race in the opening sequence. Note how the opening sequence alternates between awesome and funny with every shot?
Columbus revealing his greatest fear while sitting on a toilet when a Monster Clown bursts out from under the door (fortunately its only his imagination).
No mention of the stereotypical Suburban Mom Van being mobbed by an army of small zombie princesses?
During the driving montage, the brief shot of Little Rock explaining how Hannah Montana works to a surprisingly enthralled Tallahassee. With "Popular" byKristin Chenoweth playing in the background.
And the bit of the montage where Little Rock is driving.
Wichita: "This is the freeway, so you can go up to 65, but you don't want to go over 75..."
Columbus: "You don't want to go over 20!"
On repeated viewings, when you realise that the guy who gets killed in the bathroom to demonstrate rule #3 is the same guy who gets conned by Wichita and Little Rock in their flashback.
After the girls run off again:
Columbus: To Tallahasee You're like a giant cockblocking robot built in a secret fucking government lab.
After Little Rock takes them hostage a second time, Tallahassee shrieks "Don't kill me with my own gun!"
When Columbus finally overcomes his coulrophobia by smashing in the face of a zombie clown with a sledgehammer, the impact of the blow causes a comical clown nose *Honk*.
Tallahassee: I've never been good with goodbyes so... That'll do pig.
The appearances of the rules on screen when they're applied. The words appear on the screen, always in a manner appropriate to the scene - and when "Enjoy the little things" floats over a destroyed tacky souvenir shop, cracking, creaking and the word 'things' about to fall off the sentence at any moment...it's a hilarious visual gag.
Even better is the rule #1 Cardio.
As Columbus runs from the zombies at the gas station, the rule appears and one of the zombies smashes hip-first into the rule nad breaks it. In lap two, that zombie is limping far behind.
Columbus giving both barrels to not-actually-zombie Bill Murray.
Columbus: * holding a blender as a weapon* Now listen, 406, I don't want to hurt you but—
* blender falls apart*
Columbus: "...Shit."
"You've never heard of Willie Nelson?" "No." "Willie. Nelson."
Later...
Little Rock: Who's Bill Murray?
Tallahassee: ...I've never hit a child, but asking who Bill Murray is?? That's like asking who Gandhi is!!
Little Rock: ...who's Gandhi?
"Blind spots are for other drivers!"
How about when Columbus and Tallahassee are talking about the last time they got laid and they see a zombie in the middle of the road eating a person?
Tallahassee: Look, whatever you have waitin' for you in Columbus, I promise you it ain't any prettier then our friend here enjoying her manwich.
Tallahassee then steers the Cadillac around, driving at a reasonable speed and opens the door, smacking the zombie in the face while he laughs.
"Somebody's ear is in danger of having hair brushed over it!"
Columbus chucking the whiskey out the car window is done so perfectly, it's probably the best example of quickly-disposing-of-stuff-whilst-other-person-ain't-looking on film.
Tallahassee's verbal backtrack:
Tallahassee: [Pacific Playland] totally blows!
[Little Rock and Wichita give Tallahassee angry looks]
Tallahassee: ... my mind. Just fun for the whole family.
"Oh. My. God. You're thinking about fucking Wichita. Well, wish granted, boy! She's been fucking us for the past 24 hours!"
Wichita punking Columbus for the second time and going Bummer.
Columbus' final stand off with a zombie clown. The scenario is hilarious enough, but what he says before we see the clown is what sells it.
