A TV ad for the pre-order version of Assassin's Creed: Revelations is normal. But a TV ad for the pre-order version of Assassin's Creed: Revelations sung by Tobuscus? Hilarious!
From the gameplay demo (and the game proper), after finding out the Templars have raised the Great Chain, preventing Ezio from leaving Constantinople by boat. This is a chain intended to stop invading navies. Ezio's reaction?:
They raised the chain for me?
Ezio remembering his philandering days:
Ezio: When I was your age my interests were... (distracted by a beautiful woman note Sofia) were mainly... Salve. (hello)
Suleiman I: Incredible. I am surprised you got anything done.
Ezio: As was my mother.
Also, Ezio's attempt at wooing the aforementioned beautiful woman:
Suleiman: It is a relief to see you again, il mio bel menestrello (my handsome minstrel). Did I say that right?
Ezio: Well enough.
The kick is (as Suleiman's uncle berates the guard captain) that some foreign minstrel save Suleiman from assassination while royal guards can't.
Duccio, of all people, appear in this game for a short while. Found attempting to woo Sofia Sartor (who isn't pleased) until Ezio pops up from behind:
Duccio:[he recognizes you] Ah! Il diavolo in persona! (The devil himself!) Stay back!
Ezio: Duccio. A pleasure.
You can also still find him in the city afterward and beat him up. It gives an achievement.
Also worth mentioning is that Duccio is positively terrified - no bravado or attempts to insult Claudia - and actually warns an amused Sofia to run, too.
The fact Desmond created a drink called the "Shirley Templar" when he was a bartender.
There's a creepy part, though: the drink is a Shirley Temple with a squirt of gin. A kid's fantasy for adults, like he thought the Templars were... until they kidnapped him as easily as they would pick up some change from a sidewalk.
During one of the Desmond sequences he discusses how he ended up in New York. Apparently he was following some advice he heard somewhere saying:
Nameless Voice: Go to New York. That way, if you go there with nothing, and you leave with nothing, no one will ask why, and if you leave with something, you're one lucky son of a bitch.
In one mission, Ezio helps the Romanies get back their coin chest. What makes it funny is that you take advantage of your poison darts and spread the rumor of a 'Romani curse'. As more and more people die from the poison darts, the guards start running away. Eventually, you pick the chest up and return it to the Romani camp. As you do so, all the guards run screaming from the 'cursed chest' while Ezio and the Romanies' leader idly chit-chat with their screams in the background.
The mission where you track down and kill Manuel has Ezio cause chaos in the city to flush him out. Manuel emerges on a rooftop to address the people.
Manuel: Citizens! Soldiers! Compose yourselves. Do not give in to fear! We are the true shepherds of Constantinopolis. We are the lords of this land. We are Byzantines. Kouráyo! (Have courage!) Stand fast! Do not let anyone break your—(*sees Ezio approaching*)—Ah, skatá. (Shit.)"
Disarming opponents in the fourth Altaďr mission. Who knew seeing an 82 year old man kick someone in the balls was so utterly hilarious?
Unlocking the Desmond skin before beating the main storyline, then playing through the rest of the game with it. It even sticks around for cutscenes, with no redubbing of the voice!
Even better, it maintains Desmond's outfit perfectly and includes all the weapons... Except the Hookblade. Which becomes utterly hilarious when you see Desmond flying through the air without a connection to anything, stabbing through a Mook with his fingers, or throwing them with what looks like The Force. Desmond is a Jedi!
From the herald: "To all visitors from Transylvania looking for the head of Voivode Dracula: Yes, we have it. Yes, he's dead. No, you cannot see it. No, he will not return and invade you again. It has been over thirty years, please stop pestering us."
This gem from Clay's description of Digenes Akritas: