I have just one word (ok 2 words)
Parking Brake!
I was 15 and messing around in my sister's boyfriends vw bus.
I thought it would be funny to give him a start and turn the key he left in the ignition.
It lurched forward a foot, which was 3 inches shy of the car parked Infront of it.
I booked it out of there in a hurry!
I would much rather have something to prevent the engine from turning over while in gear and/or without the clutch depressed