Looks like a good thread to post my tale in .....

In 2004, I lived in Atlanta and had a slanted driveway.
I had my 1990 GMC Suburban up on front ramps and had NOT chocked the rear wheels, or engaged the emergency brake. ( how stupid can you be ? )
I was under the 'burb on a shop trolley to change out the intermediate drive shaft bearing ( noisy ), and all went well until I attempted to disconnect the drive shaft at the differential.
The bolts came out OK, but I could not disengage the universal bearings. Being the genius I am, I rolled out, got a pry bar and popped back under. Well, the pry bar worked just fine, I popped the drive shaft loose and it immediately starts rolling down off the ramps and down the driveway with me under it.
I had maybe 3 or 4 seconds to make a decision, I pulled my self out using whatever I could grip on the undercarriage, and almost made it unscathed.
Unfortunately, my left foot didn't make it - it got caught under the front wheel.
I know this sounds bad, but in fact it was the best thing that could have happened - it acted as a chock and stopped the truck just before it left the driveway and entered the street.
So, here I am, left foot caught under the front wheel and can't move. An angel in the form of a 250 pound plumber just happened to be passing by, he stopped and came to help.
First he asks if the keys are in the ignition, I tell him yes, but it won't do any good as the drive shaft is disconnected. He then opened the drivers door and pushed the Suburban far enough up the slanted driveway to release my foot, then hopped in and engaged the emergency brakes. ( have you ever tried to push a Suburban on even level ground ? )
The final result is I just lost some skin and didn't break anything.
I was EXTREMELY lucky !!! I should have been killed or severely maimed.
You can imagine that now anytime I get under a car ( or the Suburban, which I still have ), every chock and jack stand I own is in place and double checked.