Dying while taking a selfie. When your vanity collides with the Darwin Awards.
Can be used literally (an actual fatality) or metaphorically (such as a career- or relationship-ending idiocy).
"In recent years, more people have died of selfiecide than by shark attacks."
"So when HR found out about the pictures from the convention, he was marched out with his personal effects in a cardboard box before lunchtime. Gotta say, that was a total selfiecide, dude."