Ok Ill take a stab at it. There are actually two I have in mind:
1. A mill in Providence RI. The adjective might be OLD! This had a 600V ungrounded service. Wait, dont scroll down out of boredom yet, it gets more interesting. The Utility transformers feeding the building were sitting on the ground in a vestibule behind a locked chain link gate. They were big, about 5-6 feet tall, I dont know the KVA. Primary was underground 11KV (according to one of the lineman). IT was pretty cool in that vestibule, looked like a min sub station with racks and busbars on the wall, just a few feet behind the gate. The building next door was fed off that too. The building was a slow moving project with not much going on so the only thing the 600V did was run a transformer for work power and lights, and it also fed the elevator, which worked sometimes. I remember some of the guys would have to go to the roof top elevator room and push the contactor in with wooden stick sometimes. Yikes. At some point national grid started getting really uncomfortable with those transformers there, so they took them out and refed the building with a 600V pole bank, still ungrounded. Several years later, I finally got the go ahead from the owner to upgrade the service to a 208Y/120. I never did get paid for the job, about 16k mostly labor fortunately. OH well, it maybe almost worth the experience working on it.
2. My house! I have mentioned this before on this forum so likely some will remember. Several adjectives could apply here. Lets start with CREATIVE. I really price busted this. I take service at regular 120/240, then step it up to 2400 MGN. Wire is #10 CU 2 KV PV wire. That isnt the sketchy part, if you look into it, that wire has plenty of dielectric strength to run at 2.4KV. This goes 1900 feet to a transformer where the MV feeds out of the loop feed bushing another 600V to the solar system, and the 120/240 feeds the house. A couple funny pictures, Anyone who has done or seen any MV cable work will get a kick out of that small wire coming out of the load break elbow. And a part of the 2.4KV run that is tied to trees with some romex! Im really trying to get that last little bit buried (note its just the last 100 feet that is temporarily run in trees, the rest is buried).