Assassin's Creed: Brotherhood was the first AC game to introduce a multiplayer mode; I love its gameplay trailer. This trailer is atypical because rather than editing together footage captured while someone played the game, or making an expensive Hollywood production quality cinematic, it's more of a short film made using the game's engine. This allowed the trailer creators to play with: custom camera movements, framing, slow motion, rack focus, some custom animation, and some more I'm probably not noticing.
The trailer opens by setting the scene with a brief voiceover by the modern Templars, then we get right into it with the opening notes of We Want War" by These New Puritans. There's a slow motion shot of a nobleman running; it's revealed in a wide shot that he's being chased by a prowler. After a few rooftop leaps, the nobleman escapes with a smoke bomb.
The nobleman then calmly walks past a courtesan who turns out to be an executioner who then assassinates him. The prowler immediately climbs down from the rooftops, and assassinates the executioner.
Next we see a barber walking calmly, occasionally checking behind him to see a harlequin gaining on him. Somehow the barber gains the advantage, and slits the harlequin's throat. Elsewhere we see a doctor assassinating someone, and then we see a priest in a town square. The barber attacks the prowler only to reveal that he was an illusion. The real prowler observes from above, and gets the jump on the barber.
Finally the prowler sees the priest and doctor converging on him, and the trailer ends on a bird's eye view shot of the town square.
Describing the events of this trailer isn't really that interesting. I could just as easily say that it's about characters assassinating each other one after another. The direction, editing and music of this trailer are what make it amazing. This is a story that shows you what the experience of the multiplayer mode feels like rather than what it actually looks like while playing. Except for some custom animation, everything in this trailer can happen in-game.
Not many game trailers get made in-engine like this, especially not to this level of style and polish. I think the direction and editing of this trailer is just phenomenal. In fact, this trailer made such an impression with its filmmaking and music, that I'm pretty sure a lot of people didn't even realize that Brotherhood was even a full on Assassin's Creed game that continued Ezio's storyline.
I aspire to make something as great as this trailer someday; this sort of production requires a lot of time, effort, vision, access to the proper debug tools, and also amazing music. This trailer is a fantastic example of how it's possible to create a gameplay trailer that fakes everything for the sake of style, yet remains true to the essence of the game.
Oftentimes I see people lament that a trailer doesn't have gameplay; I think what they usually mean is they don't understand what you do in the game. Yes, there are people who won't be convinced you're showing gameplay unless they see HUD or UI elements, but I think understanding the "what?" is more important than the "how?"
The trailers I edited for the game Absolver were mostly custom cinematic scenes with some gameplay sprinkled in. There isn't any gameplay until 26 seconds in, and yet I saw a highly upvoted comment about how refreshing it is to see a trailer that was all gameplay. For gameplay trailers, I think the audience wants to see the parts which they'll have control over; the trick is showing that to them in the most interesting way possible.
It's also interesting to contrast this trailer with the Multiplayer Launch Trailer which to my eyes looks more like a typical gameplay trailer with some debug camera options for custom camera angles, but you can tell the direction is much less thought out.
It is also possible the reason the first trailer is so directed is because the gameplay systems were not finished at the time the trailer was released, so it was necessary to fake everything. A LOT of things can happen in a few months of game development.