leaving the car unlocked and unattended
used the wrong fuel (petrol in a diesel car will destroy the engine!)
driving through floods, cyclone, bushfire or other natural disaster
driving in hail storms or leaving it outside in hail storm
damage due to accumulation of mud or dirt when used in mining areas
drunk driving
using the vehicle for racing or towing, or is being towed without permission
you allowed an unauthorised person to drive the car (ie. not specified in the contract)
careless driving such as driving over gutters damaging undercarriage or wheels
driving the car after a collision without the rental company's approval