Okay, this one's a bit long, but worth it. It could be the meanest practical joke this side of those fake winning scratch-off tickets.
A guy proposes to his girlfriend on the jumbotron at Yankee Stadium. Only he didn't really want to propose. His friend just did it for him.
The main obstacle to enjoying this clip is getting over what a douche the guy pulling the prank is.
Okay, another obstacle to enjoying the clip is the screwed up synching of the sound (or lack thereof). Just watch the video in the link rather than the embedded one.
Jeez, that was aweful. I'm glad I know what that dude looks like so if I ever see him on the street I can call him out for what he is -- douchebag!