Really, all of the game's dialogue would be on this page, but to be specific...
For some, the first spoken line in the game is one.
Isaac Wassup, motherfucker?
"You ever gonna tell anyone what that fuckin' 'G' stands for?" G's response is simply "No."
The door opens up to a staircase, and a severed head rolls down it...
Isaac: Shit, man! That ain't right!
When Isaac calls G "diaper-shit".
Isaac and G are about to ride off in Isaac's car, also known as his pride and joy. Said "pride and joy" promptlyblows up.
After The Screamer is defeated, Isaac and G notice that there is a phone ringing from inside of her. Isaac refuses to open her up, because he "manicured only yesterday" and isn't about to stain a freshly-manicured set of nails with it.
This exchange in "Carny", once G and Isaac meet their first "football" mutants:
G: -in a grim tone- Here comes another bundle of joy...
In The Typing of the Dead: Overkill, the final battle allows you to "type anything, as long as you type like a motherfucker." This can go so many ways. You can kill Mother in ways including, but not limited to: swearing her out, hurling insults at her, and breaking out the Character Filibuster.
This little exchange from Overkill:
Washington: "Can I drive?" G: "NO!" Washington: "Can I have a lollipop?" G: "...Yes."
HOTD 2's voice-acting in general.
G's face when Warden Darling decides to go back to the womb.
Isaac talks tough to a zombie and kicks him. Then the zombie sits up and throws up on him.
MISSING REEL! (Sorry for the inconvenience)
Typing of the Dead
The entire game is one big Funny Moment, especially due to some of the weird phrases you have to type, or getting a word or phrase that's perfect for the situation (like a zombie jumping out of nowhere and forcing you to type "Boo!")
The Tower in Mission 3 gives the player questions, and then asks them to type the right answer. One of the possible answers to "Which of these is bigger than a bread box?" is "Yeast infection."
The question-and-answer format of the Tower? It's reused again for the final phase of The Emperor. This time, all three possible answers to each question are "correct" (however, they influence which ending you get). The answers range from semi-serious to outright silly. Some of the example questions are:
Goldman jumping off the building like in the original HotD 2, followed by an explosion and James's Stunned Silence.
Goldman bungee-jumping off the building, bouncing back up, and then burping.
Goldman letting it rip and then taking off into the sky, again with James's speechless reaction.
The credits sequence, which replaces the ending theme with one of the stage themes and shows a row of glass tubes. Typing the staff names out causes one of the zombies to break out of their tube and start dancing. By the end, the entire row is dancing.
Whenever you see a character in Typing of the Dead running around with keyboards strapped around their neck. It's especially absurd since they're killing zombies with them (somehow).