For me, Masaomi's recap of the first time he saw Anri had me cracking up.
Masaomi: Cute smile... bitchin' boobs... ! Okay, so maybe she wasn't smiling...
Really, all of Episode 6 is a CMOF, from the kidnappers spilling chloroform on themselves to Togusa's face at the concert to Kadota forgetting to keep his internal monolouge internal to "Sparkling naked~!" to Shizuo throwing a plastic elephant at Izaya...and also, the dog.
We're now part of that street gang everyone's been talking about!
Izaya stomping on the back of a thug, then following Mikado home with Celty making motorcycle noises all the way.
No, Izaya was jumping up and down on the thug, laughing happily. That was most definitely funny. I couldn't stop laughing.
When Mikado mistakenly assumes Anri was a stalker, his Internal Puppet Show plays out the possible scenarious, including a Yandere Anri coming after him with a knife - "I love you!", lighting up his home - "Fire!", and kidnapping his parents.
In episode 11, Isaac and Miria are apparently members of the Dollars. This being Isaac and Miria, even a minor cameo manages to be amusing.
In the epilogue of episode 12, Mikado works up the courage to ask Anri out, finds Kida trying to flirt with her, and, finally fed up with it, lays him out on the ground with a kick.
"Call me 'daddy!'" (Holds up sign)
The Chase Scene in episode 24 combines this with Crowning Moment of Awesome, mostly because Horada and his lackeys are completely out of their league against Shizuo and Celty, and their faces when they realize it...! Celty "seducing" Shinra later on is also pretty dang hilarious.
"Why is there a street sign in the middle of the road?"
Episode 3: "Sooo... let's go pick up chicks!" Already one of Masaomi's funniest non-sequiturs, immediately followed by a Match Cut to him attempting to pick up girls. Adult women. From their point of view.
Also in this episode, Shizuo's punch sends a gang member flying through the air, and his clothes fly off!
Crispin: I mean, I don't know who this clown is who's walking around like an eskimo...[braking tires are heard as the camera closes in on the DRRR poster behind him. wait...that sounds familiar...]
Johnny: ...[Izaya's parka] is really hip, especially with eskimos...
In one of the early episode, out of nowhere, a trash can flies from off-screen to hit Izaya in the face, sending him sprawling on the ground. Kida cringes but Mikado just stares.
In chapter 10 of the manga, there's a comedic page featuring Harima and her six phases of stalking. Let's just say it goes from Harima's victim showing natural human kindness to Harima following the poor guy on a family vacation.[1]
In episode 7, Shizuo gets fired from one of his jobs by beating up the Power Rangers. Made all the more hilarious when you realize that Izaya's voice actor was a former Power Ranger.
Shinra's Ha Ha Ha No moment after Izaya trolls him by handing his cellphone number to the police.
Izaya: How was it? Gave you quite the adrenaline shot, didn't it? Did you and Celty just grow to love each other even more due to the misattribution of arousal? Shinra: Ah hah hah. Go die chest-first in a clay ice shaver, Izaya.
Episode 12.5, Izaya tells some guys that Shizuo stole something from them... This goes about as well for them as you'd expect, and as they're flying out the window in plain view of everyone, Izaya remarks:
*to Izaya, on the phone* "Let me guess, he just happened to live in Ikebukuro, and he just happened to see him on TV, and that's why he came by. And he just happened to bring a knife with him, too! Tch... you just wanna sleep with me, don't you?"
In episode 14, Shingen is trying to cheapskate his way out of paying Celty for transporting him. Celty uses her darkness ... stuff to wrap Shingen's neck in thorny vines.
Shingen: "I was just testing you, Celty-kun. If you release me now - Ow ow ow they're poking me! Those pointy shadow things pricked me a little! Shinra! I am in grave danger here!" (struggling) "If you are my son, you should know what you need to do!"
Shinra: "Of course I do" (pickpockets Shingen's wallet and throws it to Celty)
And right after it, as Shinra declares that he would be happy if Celty stole his soul, she blows a heart-shape from her head smoke.
The final episode has Izaya getting a shiner from Simon.
Whenever Erika has a Yaoi Fangirl moment. She has shown a particular liking for a Shizuo/Izaya pairing as shown when Shizuo says he's going to Izaya's place (to murder him...) and she sparkles with blush stickers saying that he must love him. Everyone (Celty and Kadota's group) cuts her off with a Big "NO!".
Shizuo: I'm off to Shinjuku to murder Izaya.
Erika: Hey, hey! Shizu-chan's definitely in love with Izaya. Two guys... Like BL!
Celty, Togusa, Dotachin and Walker: No!
Simon trying to get his Russia Sushi signs in front of the TV cameras.