Sorry, link here.
Don’t know if this has been mentioned, but I can’t stop laughing. Ultra-simple execution, and a wonderful clip in its own right (Sesame Street flashback), so very very funny overall. 
“When you see an actor you know it’s him…because they’re unemployed”
“You see that actor and you are like him…no use to anyone.”
Fucking hilarious, I’m crying here.
From the 60’s, a commercial for the game Pie Face. (Note: sound is poor so you’ll have to turn up your volume.)
Although one of my earliest TV memories is seeing this commercial, I never had this game. Did anyone else have it?
The Hobbit!
White trash plucks an ingrown pube!
Australian professional atheist John Safran knocks on doors in Salt Lake City
The Avalanches - Frontier Psychiatrist. The height of music video absurdity.
Japanese robot dances in the streets.
Be careful who you drink with!
A classic battle of wills and the conclusion (I think).
These are very old, so some of you may have seen these before, but I just looked at them for the first time a couple days ago and found them funny: GI Joe Public Service Announcement Parodies
Game over, yeeeeeeeeeeeah!
The Top Gear American Road Trip!
(not YouTube, but still…)
http://www.findinternettv.com/Video,item,398217172.aspx
http://www.findinternettv.com/Video,item,1293198793.aspx
http://www.findinternettv.com/Video,item,1318723566.aspx
http://www.findinternettv.com/Video,item,52891473.aspx
http://www.findinternettv.com/Video,item,1416065577.aspx
http://www.findinternettv.com/Video,item,2260657827.aspx
hilarious:
john.he.is.
borderline NSFW: The Wii Dong!
This video is great! I already liked the Avalanches, this just improves their standing…
I don’t think this concept is too far off!
I must’ve managed to forget this one last time I posted on this thread, but I remembered it again now.
This is the freakiest music video I’ve ever seen.
I like this comment:
"wow, reading everyone’s comments was more amusing then watching the video itself… but holy f**, what would ever compel a human being to make something so awful"*
I had never seen nor heard about this show before, but it is fantastic. I’m not a car guy in the least, but their trip had me in stitches, especially when they drove through Alabama.
Thanks for those!
The greatest cover version of “Hey Jude” ever recorded.
Korean kids are so damn cute!
Holy crap that was a cute kid! I forwarded it.
Star Wars as reviewed by a 3-year old.
Don’t talk back to Darth Vader!
I don’t think I saw anyone post this one… the Amazing Music Machine… this video mesmorized me for hours (it’s been around for years though):
In the comments for the Cat Vs Rabbit video someone wrote “Somebody call the Chickens!” 
My contribution. I don’t know if this has been posted yet.