I'll take a photo of it later as it's sitting at home but I've been using the same Kryptonite New York Chain for 20 years now with an unusual lock that it did not come with. The reason for the mention of the lock is it was something my dad had laying around and, thanks to its design, is NOT the skinniest link on the whole setup but rather the thickest. For those who don't know what the New York Chain is, it's a 6 foot (might actually be 5 feet), 15 pound, hardened, square link chain. I'm not a fan of my bike or either of the wheels being stolen and I often need to lock to something that isn't u-lock friendly. I also used to lock my bike up at a few different college campuses back in the day as well as some fairly sketchy parts of San Francisco and Oakland. I carry it like a sash around my shoulder or in a backpack. My friends nicknamed it the chain of command.
Don't care that it's heavy, it's a small price to pay for basically a guarantee that people won't mess with it. I know it's saved my bikes numerous times. Years ago, I came out from class with friends and we went to grab our bikes. Most on the rack had been stolen, including both of my friend's bikes, but mine was one of the few left alone.
When it comes to commuting these days, I don't actually bring the lock with me since I can park my bike in my stall. However, in days past when that wasn't an option, the lock came with me every day. The lock is still used today though as I need it when I go shopping or run errands around town.