When I was living in Boulder I agreed to take a guy from Wisconsin up the Rigid Designator in Vail. The Designator is WI5 and since I didn't know how good an ice climber the guy was I suggested the Spiral Staircase next door which is WI4 as a warmup.
I am halfway up the first pitch when I break off a dinner plate chunk of ice. As SOP, I pin the ice to my chest, set my two tools and feet and let the guy know that a big piece of ice is going to be coming down. I let the ice go and the next thing I know I am holding both our body weights on my tools. In attempting to get out of the way of the ice the guy had fallen off the belay ledge.
I get to the top and start to bring him up. I ask him how it is going. He replies, 'piece of cake' and the next thing I know he takes a fall.
The final straw was right near the top of the pitch. He is trying to get a tool placement in a wide, thick sheet of ice by swinging his pick right next to my two, brand new 9mm ropes. Next thing I know, he puts a pick right through one of the ropes.
We top out and he asks if we are heading over to the Designator. We head down. It turns out it wasn't all bad. The guy bought me a new rope.
This story is somewhat infamous in central texas, and others who recognize it are welcome to correct or fill in missing details, as it happened about 25 years ago. While I was not present nor the guide, I did get a firsthand account from one of the other clients, and I had guided him once on rock and knew him well enough.
So, our Client A is the owner of an outdoor gear shop, and by and large a real nice guy who just wants to be in on the scene. He's a bit overweight and out of shape and has next to no climbing experience. He, with a couple other locals both younger and in better shape, signs up for a mountaineering course in the Cascades on Mt. Baker.
They arrive the day or two before the guide does, purchase any number of supplies, pack up a bunch of food, and decide they'll cache their day food along the approach somewhere to temporarily lighten their loads. Of course, they assume their route wil be on the north side of the mountain and wouldn't you know it, the guide's idea is the south side. That food goes to waste and they're forced to quickly resupply their day food requirement that now includes lots of candy bars.
On the hike up the mountain, the guide notices that Client A is not removing his outerwear in order to maintain proper body temperature. The guide repeatedly warns Client A that he will overheat and should remove some outerwear, but Client A, being the knowledgeable owner of an outdoor retail store, confidently replies "this is the good sh#t, it'll kick in any minute now," being that new-fangled fancy gore-tex stuff don't you know. I don't think he ever took it off on the hike up and of course he paid for it.
They set up a camp on the snow somewhere, and next day when it came time to do their instruction on glissading or whatever the guide started them with, our Client A was in no shape to leave the tent. So, they left him with instructions to take care of himself and went off to practice. When they returned to camp, Client A had spent the entire day inside the closed-up tent overheating and had removed all his clothes in an effort to cool off. He was at that point somewhat delirious and dehydrated. They found him naked in the tent having eaten every single chocolate candy bar the team had taken for the trip, leaving candy wrappers strewn throughout inside the tent.