Actually, most of my funny SH4 moments happen in RL...while playing SH4...
lets see...
RFB once got me so jumpy...my phone rang next to my hand and i jumped, resulting in me falling off my PC chair to my friends death by laughter
When eating dinner downstairs, I live on the upper floor, I would leave my volume turned up to the point where I could hear it downstairs, Imagine my parents' confusion when you would hear a muffled "ship spotted" followed by their son setting his food down and tearing up the stairs
I once forgot to reset my X-Y coords when i would import a model so i would load up the game and discover to my horror that my sub is sticking halfway out of the water
EDIT:
@Mush, i fell out of my chair laughing when i saw that picture, thats a movie you really only want to see twice.