While playing Resident Evil 4, my dad started up a chainsaw and I freaked out in the game and started shooting everything. I set off a few of those bombs that where attached to trees.
Once when playing Metroid Prime, I was low on health and then everything got dark and quiet. There was nothing but the sound of low health beeping and then CHOZO GHOST! My adrenaline shot up. My heart was litterally pounding at my chest.