Funny / Nullmetal Alchemist
Pretty much everything that comes out of Roy's mouth.
This exchange in Episode 4:
Edward: Majhal? Majhal!
Guard: Y-yes, Ma-
Edward:Al, get my top hat.
Al: But you don't have a-
Edward: THEN I'LL MAKE ONE! (does so) Magic just got real.
Nina is like a bite-sized, hyperactive druggie. And it is glorious.
A darkly humorous example:
Tucker: [The Chimera] talks!
Tucker: See? It said bark!
Ed: Wait, what kind of animals did you use?
Tucker: Oh, just some regular old animals I found lying around the house...
Tucker: Um...a dog might have been one of them—
Tucker: And Nina.
At the end of Episode 6, Scar accidentally kills Nina. He responds by vomiting for an insanely long time while "Spanish Flea" plays in the background.
Scar: Oh god! This is why I can't have nice things!
Hughes' discussion on his sex life:
"But since we're on the subject of apparel: guess who was wearing a french maid outfit last night? I felt so sexy."
Mustang's "get over it" speech to Edward on Nina's death which ends up with him singing " It's the circle of life!"
"She's in a better place. Like your lungs! Bits of her blood are in the air and are now quite literally a part of you! And not just in some stupid pansy ass poetic way. And then the seagulls will eat the flesh, and when they die, they'll feed the plants! And you know who eats plants? Vegetarians, the lowest rung of life itself! It goes on and on forever, Edward. It's the ciiircle of liiiife~"
"Detective Dick, I demand you look at her tits!" It Makes Sense in Context, but that doesn't stop it from being hilarious.
"Happy Make Fun of Mexicans Day!", which Crosses the Line Twice.
"Edward Elric Yo." Just...all of it. Every last lyric is hysterical.
In episode 11, when Ed first saw Juliet Douglas aka Sloth, we got this line after seeing images of his mother.
Edward: It's... PSYREN!
From the same episode: when Ed is introduced for his and Roy's duel, you can hear "I'm a Little Teapot" playing in the background.
The barking cat deserves a mention.
Al's cat. It came with the rain, a cellphone, does its own taxes, and had the power to piss off Mustang and take away Al's Only Sane Man status. It also barks, for some reason.
The "town gimmick" Running Gag.
"He's carrots?" "He's carrots!" "He's carrots!" "He's carrots." "Why is he carrots?" "'Cos he is!" "..." "Goodbye!"