Let's see...
During my medic internship I had the Lifepak 12 plugged into the inverter while en route to the hospital. Forgot to unplug it when pulling the gurney out of the back of the RA. Eventually the tension on the cable exceeded the strength of the electrodes' attachment to our patient...all the electrodes ripped away from the patient's body while the monitor plummeted from the back of the gurney causing much more of a deafening crash than you'd expect when colliding with the tailboard of the ambulance. I looked at my preceptor in horror as he reached down to grab the monitor. Amazingly it was unscathed (with the sound it made I was expecting it to be in shambles on the ground, like a porcelain vase or something) and worked fine after we reconnected it to our startled patient. Had a bit of a talking to after that little episode to say the least.
Again, during my internship I left my preceptor's clipboard on the photocopier at one of the hospitals we go to. Didn't realize it till we got another call and my preceptor said, "Hey, where's my clipboard?" To add insult to injury there weren't any spare PCRs in the RA...my preceptor had to write everything down on a blank white sheet of printer paper (don't know where found this). Luckily we transported to the same hospital and the clipboard with all the PCRs in it was still sitting on top of the photocopier...same thing happened again later that day but the second time it was his fault!
OK, this didn't happen during my internship. Had a Zoll M Series go absolutely bonkers on me for no conceivable reason. Attached monitor to a young, athletic female patient and as soon as I switched it to Lead II some sort of insane artifact caused the HR counter on it to soar into the upper 300's (there weren't any distinct "beeps" for the HR anymore...it sounded like an alarm almost). The waveform was an unidentifiable and nearly solid yellow block from the artifact spikes occurring so ridiculously close together. This same thing happened in all leads except pads (which, naturally, showed nothing as they weren't connected). Nothing I did to troubleshoot this worked. Had the patient's RN standing next to me watching disapprovingly. EMT partner looking at me helpless and confused. Finally i just turned it off, got in the back of the rig, replaced all the electrode patches and replaced the battery (despite it being a brand new battery) on the monitor. Magically when I turned it back on I had a perfect, textbook sinus rhythm waveform...I hate Zolls.