Back in the day (we're talking serious old school here), we were playing Call of Cthulu.
We're in the Great North Woods, looking for something strange.
About 8 of us walking in line through the forest, when the GM says,
"Make a perception check."
We all failed, except the guy armed with the 30-06 rifle.
The GM tells him "You see a puma in a tree,ready to leap on the party. You get one action. What do you do?"
He says, "I shout out, 'Look! A Puma!'" In those days, the shout counted as his action. His chance to negate the surprise is spent, and the puma has the intiative, and goes next. The puma jumps on my character and makes a successful sneak attack. Claw, claw, bite, double damage all round, and I'm dead.
Actually more embarassing for the other guy than for me, but I'm the one who died.