I've got two I encountered last night, on this the eve of my second play-through.
First was a little east-southeast of Satellite Station Olivia, on Hard mode. I was sneaking among the rocks and spotted a toppled fridge, so I went to investigate. Got ambushed by some molerats, then I heard a high-pitched beeping like a SM Suicider! All of a sudden the molerat that was charging me exploded! Who knew they could do that?
Second was when I was wrapping up for the night, and trying to get to Relay Tower 3SM-U81 (east of Ten Pines Bluff.). Spotted the raiders camped out there, started taking pot-shots, and Dogmeat got into the action. Saw the tell-tale headlamp of a raider in power armor, and as I dropped into VATS to give him a facefull of lead, I heard the frightening whine of a mini-nuke launched from a fat man! Got my two shots off and still managed to dodge the nuke, switched to my shotgun, and approached Boomer with caution while my faithful pup kept him occupied. Then he evidently decides that there's only ONE way to get a pissed-off Alsatian off his junk, and that's to lob a nuke at his feet! Took us all out, and left me going LOLWUT!?