Oliver tries to convince Diggle to join his crusade, then ditches his new bodyguard Rob when he shows up, leading to the following exchange.
Oliver: Gotta use the bathroom.
(He leaves. Solid minute of silence before Dig turns to Rob)
Diggle: Man, that boy's long gone.
Diggle being a fanboy over Oliver's gadgets.
Diggle: Oh, that's sweet.
The quick Take That at Black Canary's infamous fishnet stockings, delivered by her comic identity no less.
When Thea starts to think that Oliver is the masked vigilante because he got her an arrowhead, he delivers this brilliant quip.
Oliver: Good thing I didn't get you the panda shot glass or you'd think I was Panda Man.
When Oliver meets Thea's boyfriend.
Oliver: Who's this Shane guy?
Thea: We rob banks and smoke crack together.
Felicity's reason for not visiting Australia: Fear of kangaroos.
Ollie's reaction when he sees Thea with a boy her age about to have sex.
Oliver (low voice, similar to Bryan Mills): Hit the road.
And he aims his hand like he was gonna shoot him.
Ollie waving off a proposed nickname for The Hood: Green Arrow. He thinks it sounded lame.
The boy mentioned above shows up (invited) at the Queen Christmas party and runs into Diggle and Ollie at the front door. While Shane and Ollie have a short chat, you can clearly see Diggle in the background slowly shaking his head. Diggle's Genre Savvy knows no bounds.
In "Year's End", Felicity saying that she doesn't understand why archery is all the rage, and that she finds it ridiculous in front of Oliver... Ah, the good old days when she didn't know better.
When Tommy visits Laurel and finds her father there in her apartment.
Tommy: Merry Christmas. How are you? Det. Lance (in a low voice): Proficient with firearms.
Later that episode, during the Queens' Christmas party, Ollie and Diggle are talking when Thea's friend, Shane, shows up with a bouquet of flowers.
Diggle: *Standing behind Ollie, just shakes his head*
Oliver being unable to pronounce Zack Galifinakis' last name.
When Oliver asks Felicity to analyze some Vertigo for him, he tries to pass it off as a "sports drink" that he's keeping in a syringe because he "ran out of sports bottles." There is about a half beat pause as everyone absorbs the ridiculousness of that lie and Diggle just walks away.
Diggle:Your B.S. stories are getting worse.
Oliver: I'm aware.
Ollie needs to kill someone in front of the Russian mob to gain their trust. Diggle is horrified, until they carry the body off to a car trunk and Ollie promptly wakes the guy up. Surprised, Diggle asks if Ollie's gonna teach him how to do it, but Ollie just says "No." and then punches the guy really hard in order to knock him out again.
Dig is spying on Moira and, to that end, replaces her chauffeur. She enters a restaurant and tells him she doesn't need an escort. Dig ends up following her anyway, expecting her to meet some evil dude, but stumbles on the birthday party of one of Moira's friends. He has to pretend to look for the restroom. What sells it is the "Happy Birthday" addressed to the friend.
This dialog snippet in "The Odyssey":
Felicity Smoak: I'm guessing how and why are Oliver Queen's least favorite questions.
John Diggle: Yeah, well, there's also when and where he's not too fond of.
Also, Felicity's obsessive attitude towards technology:
Oliver: Then why did you upgrade my system?
Felicity: Seeing a system set up that poorly hurts me. In my soul.
Also, Island!Ollie trying (and failing) to make fire for two hours, and then Slade whipping out his lighter. His answers to Ollie's protestations:
I know, I was watching you. Thank you for the entertainment.
Felicity: (helping catch the Dodger, a jewel thief, using a brooch donated by the Queen family as bait) [What are you going to do if] he absconds with your family jewels?
Also, Ollie explaining how he typically gets the information he needs (putting the fear of God into the interrogated person), and then saying that they can try Felicity's way (slipping a bug in McKenna's phone)
On the island, even while wounded and sick, Slade still has the strength to quip a bit, suggesting that Island!Ollie gets him a Maxim or Sports Illustrated while looking for Yao Fei's "Super herbs".
In "Dead to Rights":
Diggle: You may not want to go after the girl who's hunting you down.
Ollie: Well, it's slim pickings for us vigilantes.
When Malcolm visits the group.
Malcolm: They're bestowing me with their annual Humanitarian Award.
Tommy: What, they ran out of actual humans to give it to?
Also, during Tommy's birthday at Laurel's place, after she says the ringing is probably for the food that she ordered
The look on Malcolm's face when told the Hood saved him.
Slade sarcastically suggesting that Island!Ollie go gather enough bamboo to build a boat like on Gilligan's Island; later, his reaction when Ollie gets the radio working.
There's also the Visual Pun that happened in that scene. Slade had just killed a boar and brought back to eat. He says Oliver will get the radio working when pigs fly. He gets it to work, and Slade throws the pig off his shoulders, meaning at least one pig did fly.
John's calling out Oliver on the Double Standard between John and Helena. How he points it out: Would Oliver have killed John if he looked like the T-Mobile Girl?
Felicity: It's just... you went over there to be all, "Grr, stop being bad or I'll arrow you," and now you want to rescue him.
Ollie: I don't like the idea that somebody dangerous is out there.
*Felicity turns around and gives Ollie the "oh, really?" look*
A little later in the scene, Felicity notes that the purchase of UNIDAC was around the same time she and Ollie first met. The way she says it almost sounds like a perky subtle "You know, when our relationship first started. Nudge nudge wink wink."
Needing direct access to Merlyn's mainframe in his office building to find some info, Team Green Arrow sneak Felicity into the building, providing cover. Once she's finished and leaves, she runs smack dab into an unexpected security guard and Ollie's too distracted to help. Enter Diggle who's posing as a security guard.
Diggle: There you are! Thanks a lot man, this one snuck past security. One of Merlyn Jr.'s bimbos; she's pissed he never called her back.
Security Guard: Copy that. I read the tabloids.
Diggle: Yeah, thanks again. (To Felicity) Let's go, Barbie. Your new last name ain't gonna be Merlyn.
Felicity: (Playing along) But I love him! He's my man! (Out of earshot, grinning and giggling) My Knight in Shining Armor!
Diggle: (Grinning right back) Let's go.
Felicity is trying unsuccessfully to hack into the Merlyn mainframe. Ollie is apparently pestering her about it.
Felicity: Just for the record, I will pump my fist in the air and scream "Yes!" if I get anything.
(Later, after successfully hacking into the mainframe and downloading the info.)
Felicity: (Pumping her fist in the air) Yes! (Looks at her fist) Wow, I really do do that.
Oliver introducing himself to Roy as "Thea's disapproving older brother".
Felicity, after Oliver swings her across an empty elevator shaft and takes her to the Merlyn Global mainframe, looks a little green around the gills. She mentions that her "about to hack" face (hack the computer or hack up her lunch is left ambiguous.)
"City of Heroes" gives us a few:
Diggle and Felicity talking on the airplane:
Diggle: Felicity, if you're so scared, why did you insist on sitting up front?
Felicity: This is the only seat with a seatbelt.
Diggle: Which will come in handy when we hit the water at 180 miles an hour.
*Terrified look from Felicity*
Diggle: Which will not happen.
Felicity throwing up after skydiving.
And Diggle thanking her for waiting until they were on the ground to do so.
"Identity" features Oliver noting that Felicity and Diggle need secret identities to continue helping him, leading to Diggle dryly commenting that his secret identity is the black driver. Which Oliver later uses as a Brick Joke.
Oliver: If I'm going to be Oliver Queen CEO, then I can't very well travel down 18 floors every time you and I need to discuss how we spend our nights. Felicity: And I love spending the night with you. (She immediately realizes what she said and grimaces)
Even better, the way Oliver said that suggests that he actually said it that way just because he knew Felicity would fall for it.
Also, Felicity's refusal to take her "secretarial" job lying down.
Felicity: You know, I would [get some coffee], Mr. Queen, but it seems that someone's broken our coffeemaker. [Whispers quietly to him upon leaving] Violently.
Upon arriving in Verdant, Oliver is greeted by a surprised Thea, noting that she didn't see him arrive.
The Canary setting traps for the men that followed her to her hideout
Diggle explaining why he's willing to get arrested in a foreign country, with a hideous amount of drugs. This situation - not funny. Felicity's reaction to the situation is a completely different story.
Diggle: Felicity... Lyla isn't my friend. She was my wife.
Quentin Lance:You might wanna fill in our mutual friend in on this. Felicity: Don't worry. I'm sure he's on it. (Camera pans over to Oliver)
The funniest part, her slight grin and the awesomeness of her keeping her eyes focused on Lance.
The Running Gag with Oliver taking shots at Barry's youthful looks.
Quentin Lance: Great. Who the hell are you?
Oliver: And do your parents know you're here?
Oliver: Time for a dance?
Felicity: Not really feeling like dancing with you, Oliver.
Oliver: I know. That's why I called him. (gestures to Barry who just entered) FYI, they will card him at the bar.
Near the beginning of the episode:
Felicity: Mrs. Queen, welcome back to the company. Moira: Thank you. Felicity: You look fabulous. Really, better than ever. Did you do something to your hair? Moira: (Dryly) Yes, I shampooed it without eight women and a guard watching me. Felicity: (Awkward look) Is it ok to laugh? Because I was ordered not to say anything about you being in prison, just to avoid any awkward... (beat) exchanges. (Moira walks off) Oliver: Like that one.
Barry Allen entering with a trademark Felicity Smoak quality ramble.
Barry: Actually, it was only one guy. Uh, sorry, I'm late. But, actually my train was late. Well, the second one. The first one... I did miss, but that was my cab driver's fault. I've got this great traffic app. And he thought that...(trails off) he was right. But I'm here now, though. So...
Oliver's attempt at nonchalance when Barry asks him a...interesting hypothetical question.
Barry: I'm guessing you don't know how hard it is to break someone's neck, hmm?
Barry and Felicity discussing Ollie-as-the-Vigilante:
Barry: Police reports show that he uses carbon arrows, but if he switched to an aluminum carbon composite, he would have far better penetration. Felicity: Maybe he thinks he penetrates just fine.
Ollie is a little suspicious of Barry:
Ollie: I want you to look into this Allen kid. There's more to him than he's letting on. (Felicity and Barry are working side by side seamlessly, bumping shoulders.) Diggle: (amused) His intentions seem pretty clear to me.
Felicity: This is the point in a lifesaving emergency where you thank the person that did the lifesaving.
Felicity: Well, we didn't have time to get your vote, what with you unconscious and dying. Ollie: What happens if he leaves here and goes right to the police? Felicity: He wouldn't do that. Barry: (overlapping Felicity) I wouldn't do that. Felicity: I trust him. Ollie: I don't! Felicity: What are you going to do, put an arrow in him? Ollie: I am considering it. Felicity: Don't worry, he's kidding. (Barry does not look too comforted)
The outcome of Oliver's choice to put an arrow into Roy's thigh. After a rather uncomfortable session in front of his sister and her friends, Oliver has to remove the arrow from Roy's thigh (who was given whiskey for the pain from Sin that was poured on his leg by Ollie), and it ends with a rather... awkward call to Diggle:
Oliver: Diggle, I need you to come to the Queen mansion. (Beat) Roy's been shot ... with an arrow. (Beat) It's a... long story. Look, just bring the first aid kit to Thea's room. Thank you.
Felicity learns about Shado.
Felicity: Shado. Sara. How many women were you marooned with? Are you sure this wasn't fantasy island?
Felicity has a little fun at Barry's expense for making assumptions:
Funnier the second time around - Oliver's righteous indignation at being told to pull his head out of his ass.
Quentin and Laurel are discussing a suspicious invoice:
Laurel: I'm trying to find someone named "Maya Resik." I searched the Internet, the DMV records, social security...Nothing.
Quentin: Why are you looking for a ghost?
Laurel: Sebastian's paying her bills. A woman who doesn't seem to exist; I find that suspicious.
Quentin: Thinking that your boyfriend's up to no good, that's typically more my thing than yours.
Laurel: Oh, he's not exactly my boyfriend.
Quentin: Well, that makes digging into his life a little less fun, then.
Diggle's chagrin at being the referee between Felicity and Oliver instead of actually fighting with Oliver
Diggle: Hey, is this how it's going to be with you two from now on?
Felicity and Diggle are disarming the trigger:
Diggle: He probably put in a safeguard. Tampering with it will set off a deadman's switch.
Felicity: That's a really depressing term. (beat) And a little bit sexist.
The look on Shrapnel's face when he realizes Oliver had cut the cord to his detonator.
Arrow is interrogating a crook with the help of an audio polygraph. However, Felicity tells him that the guy needs to say the truth at least once for it to work. Cue this question, suggested by Felicity, asked by Ollie with his filtered voice, angrily:
Arrow: What color are your shoes?
Crook: What?... Blue.
Ollie is talking to Roy behind Verdant:
Ollie: It takes a lot to run towards danger, not away from it.
Walter: I'm no longer your boss, Felicity. So let's make it "Walter" from now on. Felicity: Okay. Walter.
Felicity: That is the money Mrs. Queen used to do some really bad things. I mean, you guys did get divorced for pretty good reasons. Which is not my business.
Again - situation, not funny. Felicity has found out Thea's actual parentage and was emotionally blackmailed by Moira Queen to keep her mouth shut. Oliver's physical reaction to the very weird eye contact between the two (imagine someone watching a tennis match.) - funny.
Sara's response when Quentin asks about where she met the Arrow, which he admits is Actually Pretty Funny, even as a joke.
Sara: Vigilante club.
"Time of Death":
Felicity comparing a small scar in her mouth to Ollie, Dig and Sara's battle scars.
Felicity got shot saving the Canary's life, and needs to be sewn up. Instead of going to the hospital, she insists on getting it done on the Foundry, like the others. Except that she isn't as badass, and Dig gives her oxycodone, which he pretends is aspirin. Felicity on drugs is quite a sight.
Felicity: Dig gave me some of those aspirins... are you spinning?
Upon seeing Sara for the first time since she was forced to leave Starling City, Sin promptly glomps her, much to everyone else's confusion. She quickly makes up a story about how she always does that when people come back from the dead due to a zombie fetish.
The awkward moment between Oliver and Quentin after the latter apologizes over his treatment of the former following his return a year and a half earlier. There's a beat, then Lance quickly backs out before it gets too weird.
Island!Ollie's first attempt at shooting trick arrows. Later we realize that he was just trying to show off, since there was no tactical reason for the shot.
Oliver: (flustered) There was a breeze.
When Sara explains that in order to sell Ivo on the effect of the truth serum working, Ollie's going to need to act like he's stoned, Ollie simply smirks and says he has a lot of practice at doing that.
Slade spending the whole episode in the present day trolling Oliver in the mansion, since the latter can't reveal the truth about Slade to Moira and Thea without revealing the truth about himself.
The Season Two trailer shows Diggle being introduced to the Suicide Squad, which contains Bronze Tiger, Shrapnel and Deadshot. His response:
Diggle: What, O.J and Charles Manson weren't available?
This has to deserve a mention. Note: They all have surprisingly good singing voices. It was filmed in the mixed bathrooms.
But this tops it off. Not only is Barrowman's singing really...special, but this was filmed in the "green room" and we can see Colton Haynes taking a leak! In the presence of Barrowman, Willa Holland and Emily Bett Rickards. Who filmed everything.
Colin Donnell's girlfriend, Zelda Williams, made a gallows-humor tribute to Tommy's death.