EPROM and system board in an old Telxon data collection terminal. We connected it to a DEC mini/mainframe (1989-ish) with RS232. One of the pins was high voltage from the DEC and smoked the entire Telxon unit. Left a black mark on the DEC case where the unit was sitting. When we were connecting it I was joking around saying "if you guys have a fire extinguisher around you might want it close by".....
Last time I used that joke.