Let's see:
I was running a 623 scraper building a landfill. Our spoil pile was probably 30 feet high, and we were dumping around a curve. Well, one of the dozer operators was cleaning up the toe of the slope and cut a little too much. I came around (30 feet above) and the slope gave way. Started to flip over, but got it sorta pointed downhill and rode the landslide down at what seem the speed of sound.
Was doing a small mowing job on my Yanmar 1500D with a 4' shredder. I was mowing along a ditch in about eye level grass. Well, the ditch widened, the slope got worse, and I discovered that I had forgotten to put the over-running clutch back on the PTO shaft some time or another, because the shredder pushed me onto the steeper slope... and then the yanmar flipped on its side. How I didn't get my size 11 EEEE feet stuck jumping off I'll never know. The tractor continued to run, the shredder and the back wheel continued to spin. Completely my fault on so many levels. I should have walked the job better, and should have looked over the equipment.
I was running a motor grader, cleaning up the last part of a job while my boss was loading the dozer. When he was done, he waved me over and told me once I was finished to take the haul truck (and dozer) to the yard for the night. An hour or two later, I jumped in the truck and hauled butt to the yard, because it was Friday.

Went around a corner a little fast, heard/felt a racket. Looked back and the dozer was setting on the side of the road. The boss didn't chain the dozer down, and I didn't think to look. Again, completely my fault, and I'm lucky someone didn't get killed. I'm also lucky the dozer just slid instead of flipped.
Mowing highway right of way, up on the side of an overpass and hit a hole hidden in the grass, spindle broke and I got to watch the front, downhilll side wheel of the tractor bounce down the hill, while I tried to follow it while keeping the other three wheels pointing down. If it had been a 100 feet before, I think I would have rolled it all the way down.
Bee stories:
Running a D5 clearing brush along a creek bed for a water conservation project. Knocked over a hollow tree filled with africanized bees. They covered the dozer and followed me over a mile down the creek well over a mile. Found bees in the precleaner for over week. VERY lucky I had a cab.
Running a 320 cat exavator, grubbing trees. One of them was filled with bees. Clogged up the airfilter so bad that the machine started losing power, then on the way to the truck so many covered the radiator enough to make the engine overheat. Once I got the machine next to the truck I made a mad dash to it and got stung half a dozen times.
On an underground electric job we were using a cat extendalift to pull old wire out of the ductbank. I'd lower the forks down, someone would tie the wire to the forks, and I'd shoot the forks up into the air, pulling the wire out. At the top of the boom's reach, I'd lower the wire, one grunt would cut the wire, another would tie it off again and I'd pull another length of cable out of the ground. Of course it was getting dark on friday night, we all wanted to get finished so we could drive home to Texas for the weekend (the job was in little rock) and of course a storm was blowing it. Being young, dumb and... gungho, we all kept working until the first bolt of lightning hit about a 100 yards away. Suddenly, lifting a bundle of 4/0 copper wire 30 feet into the sky seemed like a bad idea...
Just stupid:
Doing a bridge job out in the middle of no where with my father. I was running a dozer down in the creek, and him and his crew were wrecking out the old bridge. The only place to get the dozer out of the creek was half a mile down stream, and the banks were more like walls. So, during lunch times I'd take a rope sling with a bowline tied on each end. My father would lower the hook on the ancient link belt crane he was running, I'd hook the middle of the rope sling on the hoop, put my feet in the loops, grab the wirerope and he'd haul me about 100 feet up. After lunch he'd drop me back down to my dozer. There is no enough room here to list all the bad things that could have happened...