Heaviest? Lol, I think my name says it all. Bit lighter now than I was when I was given the nickname 14 years ago, thankfully, but I still top 300 when dressed to ascend w/o saws. Was the summer between Frosh & Soph years in college, 2 buddies and I took off on a rock climbing road trip. Somewhere between Devils Lake State Park in WI and Yosemite the floorboard on my station wagon finished rusting through and my harness spent a good portion of the trip laying on top of the muffler.
At the climbing store, I was having trouble finding a harness that fit. The clerk(nice guy, wound up climbing with him later that week) called around to other stores, finally found me a Misty Mountain Cadillac big wall harness in XXL from a guy who asked "Sheesh, who are you trying to fit, a sumo wrestler?" Laughter ensued and a nickname was born.
I also got a kick out of the fact that a small portion of my climbing rack was rated at strengths lower than my weight. A couple micro-aid stoppers on my rack were rated at only 1.5kn, which works out to roughly 340 pounds force. I was already 10 lbs over that in harness, shoes and skivvies, let alone after tossing on a trad rack with 15+ lbs of protection.