Any promotion, any time period. That said, the below is all WWF/WWE stuff. As much as I enjoyed classic ECW, a lot of the signs that popped up there reeked of smarky attention-whoring.
:"WASH YOUR FACE UMAGA"
"SOMEONE FEED TERRI" (referring to Terri Runnells)
"I PAID $150 TO SEE HARDCORE HOLLY"
"MORTIS IS IN GWAR"
"GET WELL SOON ANDRE THE GIANT" (from a Smackdown in 2002)
"THIS MATCH SPONSORED BY THE AARP" (for Undertaker vs. HBK at WM26)
"LASSIE IS THE ONLY GREAT COLLIE"
An entire row of people holding a bedsheet with the New Age Outlaws' "Ladies and gentlemen, boys and girls..." intro
The random "KUATO LIVES" from probably about 9 or 10 years ago (oh how I wish I had a screencap) is probably my favorite. Nonsequitur references to other forms of entertainment always win for me, as do ones that just make no sense at all ("I TILL SOIL").