The one that comes to mind was feeding trays to a conveyor belt in a food processing plant. The trays came on a stack that was from 8 inches off the ground to 6 feet, so each tray came from a different height.
The wood was so rough that I went through a pair of leather gloves in less than a day. (I eventually figured out to wrap them in duct tape while still new, and keep wrapping them whenever I got a chance.)
At least the weather was reasonable. There are comparable jobs in much hotter and much colder weather.
And then there are jobs where it's easy to lose limbs or lives.
That's not counting the gross jobs, like picking up road kill, or the emotionally draining jobs, like putting abandoned pets to sleep.