The rooftop scene in Rock Band 3 (which can be re-viewed in Customize Band > View Band History > Rooftop VIPs). You get it after getting a tour bus, and it's Exactly What It Says on the Tin: your band members are the VIPs at a rooftop party with booze (set to "Been Caught Stealing"). The climatic part of this scene is better watched than described; each bandmate has a part in it:
Tries doing a limbo dance only to fall flat on his back (to the disappointment of his bandmates and other onlookers).
Leaves the bathroom with a less-than-proud look on their face.
Though, if it's a male character, they're walking out of the Female Washroom and looking very proud.
Performs a precarious crane kick on a table (in a way that takes no skill but looks dangerous, just like a drunk would do in real life).
Shoves a fan (with all their clothes on) into the pool.
Whips a chair at someone at full-speed, cutting away before we see the chair fall into the city streets below (but it's clearly going to happen)
A chair?! It looks more like a freaking BBQ!
From a first person perspective, a very familiar scene (to anyone who's had a few too many before) in which this person starts falling down to the ground as their vision starts blurring and darkening. One imagines the possible heated debates within the animation team about exactly how the blurring and darkening was applied here.
You see your character waking up the morning after (they slept on the roof), and another bandmate sitting with their hand on their forehead, totally immobile. The other two are passed out on the floor.
In keeping with the abrupt ending of the song itself, when playing "I Want You (She's So Heavy)", the visuals cut entirely to black at the end. Expect to see several perplexed stares from bandmates if they're not aware of this in advance.
Also worth mentioning is that The Ultimate Showdown of Ultimate Destiny is available via RBN, as well as BRODYQUEST, Amazing Horse, Do You Like My Sword and I Like Trains. More internet tunes are also rumored and/or confirmed to be coming, including Mine Turtle.
Conversely, most songs require that you "sing" in a certain pitch (roughly), but they never check your voice against the lyrics or anything like that, so dedicated players can use instruments instead. A particularly comical one is someone playing the trombone in RB1 bonus song I Get By, missing only one note (and the game calls it perfect anyway).
The Rock Band Network contains Parry Gripp's "Nom Nom Nom Nom Nom Nom Nom." Enough said.
He also got the songs Girl At The Video Game Store, Last Train to Awesometown, Space Unicorn and Spaghetti Cat available. All of them just as silly as they sound.
One of the "Family Friendly" songs for Lego Rock Band is Wolfmother's "Woman". The sight of Lego minifigures rocking the hell out to that song is surreal and hilarious.
Even funnier when you realize that This Calling by All That Remains is also labeled as family friendly and playable in the game. You know, that song that starts off with a ear shattering scream, contains only growled vocals outside of the choruses AND was featured on the soundtrack to Saw III. Truly a good old family classic!
The re-recording of "Volcano" by Jimmy Buffett changes the lyric "Don't want to land on no ayatollah / I got nothin a more to say" to "I want to be a couch potato / Just play Rock Band every day."
We know that sometimes before a guitar solo, the singer may go and stage dive. Now picture that when you're playing the music video venues.
Back in 2008, the week of Rock Band 2's release, when Megadeth's Peace Sells...But Who's Buying? album released as DLC, if you went into the music store that week, it would say, "Peace sells...but who's buying? You are!" Epic lulz.
The tour mode gives you a blurb about the city you're about to perform in. Such as:
Los Angeles - "Don't go shot-for-shot with a mariachi band. That guy with the giant guitar is a ringer."
Tokyo - "If your manager can't find what you're looking for in a vending machine, your manager isn't trying hard enough."