*Playing a 40k Only War*
That one time when you failed a perception check to find out if that supposed enemy bunker was actually manned. Didnt fancy wasting a preciuos smoke grenade on a potentially empty enemy position but due to a fudged supply drop the day before knew you had plenty of toilet paper in your rucksack so proceeded to throw that at the bunker instead. Great success!
Only in doing so you had alerted a heavy bolter and las cannon and lost the element of surprise... fire fight ensues resulting in 50% casulaties to the squad, commander losing an arm and the following session being your characters court martial finding you guilty of gross incompetance and charging you to death by firing squad.
BEST GAME EVER!