Sometimes it can be the tiniest visible break in a component that releases a massive flash of light, sparks, a stench that fills the room and enough noise to skip a few heartbeats.

This was one of those - http://en.wikipedia.org/wiki/File:No_blue_smoke.jpg

I had similar happen inside a Quadra 840AV PSU - it was a voltage regulator IC, from memory. Also rather small damage for the noise, light & sound it made

Dana