Steph: I'd be fucking stoked if they weren't releasing me today!
Marble Hornets has one early on that does a good job at setting the mood: "Burn them."
For the first dozen or so videos, J was strictly a narrator and viewpoint character. After a while, he started to get a bit more involved, visiting locations and interviewing witnesses to try and piece together the mystery. Then, in 19, things happened. "I have been recording myself for a month now..."
"Season 2", like the first part, opens with Entry 27's Wham Line. "The past 7 months are completely missing from my memory."
"There is something bothering me. I don't remember any of this happening".
Entry #49: "I told you not to follow me!"
Entry #64: It's been over a year since Alex has made his presence known, some presumed him dead. When Jay and Tim go explore the tunnel in Rosswood, Jay's phone rings.
Phone: Leave. Now.
Jay: That was Alex!
Vampire Quest: "When I was a child...I...was kidnapped...by Lilicore as retribution."
Achyls: "Blow the collar! I said BLOW THE FUCKING COLLAR!"
Sparky: "It-it...it won't work, Sir!"
The final line of V3 is a massive example.
B58 - Johnathan Rizzolo - Deceased
"An attempt was made by a military organization to rescue some of the contestants in this season of Survival of the Fittest. The lives of many students were lost as a result of the actions of your governments. Any future attempts will be met with an immediate and total detonation of all collars."
This later turns out to be a rare subversion in the form of a Red Herring; it turns out that all the v4 escapees are alive and well.
Suburban Knights: "Itís Malachite. Malachite sent that chain letter. He was waiting for someone to go after Malachite's Hand."
And not ten minutes later: "Critic?" "Suede?"
In Perfect Kirby 3, Kirby tells Roy he knows about the Hippin' Jippin' Gene.
The SCP Foundation has several of these. Often an entry will lead the reader in a certain direction by deliberately not revealing all of the object's qualities; the Wham Line will then drastically change the tone of the piece. Particularly good ones are for SCP-1025, SCP-804, SCP-089, and SCP-093's associated entries.
SCP-089: "For each locution event, SCP-089-A is a healthy, unblemished human infant or child between eight months and six years of age, and SCP-089-B is that childís natural mother."
SCP-093: there was no war it was him him him him him IT. IT. it came from between the folds of time and space and worlds and light and dark something that is but should not be slipped in and called out to them as their god and they believed it and they tasted it and touched it and layed with it and became its property and did its will and IT IS STILL HERE
-In it...is everything. So many aspects of what just happened in this entire fiasco of a "competition". The Meteor. The device to stop it. The things found in Big Mt. The state of the wasteland itself. The hiring of individuals from other worlds to eliminate political enemies on this one. All cobbled together from sections of a very ancient and much bigger plan by a "Courier Six"...to eliminate anyone who would oppose his rule of New Vegas-