Favorite Beavis and Butt-Head Quote
 

"It's high noon on my sundial."

"I am the great Cornholio! I need TP for my bunghole!"

Also, the whole Mr. Buzzcut speech in the "No Laughing" episode...you know, "This is SEX EDUCATION week!"

Star Trek Fan
 

"Number One, I order you to go take a Number Two."

(You have to be a hard-core Trekkie to appreciate that one. :D )

--add

My real sister used to put her shirt up over her head and do that impression so great ! hahahah

"The angle of the dangle is adversely proportional to the heat of the beat"

Responding to a fast food restaurant customer through the drive-through intercom:
 

"Go away."