Most expensive pile-up: 8 Ferraris, 1 Lamborghini, 3 Mercedes-Benz

Happened at 10.15am (local time) on 4th December 2011 over the weekend on the Chugoku Expressway, Yamaguchi prefecture, Japan's south-west. They were travelling from Hiroshima to Kyushu (other news sites report the other way round), and were doing 140-160 km/h.

Apparently 14 vehicles were involved, including at least one car heading in the opposite direction.

Partial inventory:

Ferrari F430 (2 units, one a rare Scuderia variant)
Ferrari F355 (2 units)
Ferrari F512 (1 unit)
Ferrari F360 (2 units)
Lamborghini Diablo
Mercedes CL600 (at least 1 unit)
Nissan GT-R Skyline (Japanese supercar)
Toyota Prius

Total damage: up to USD3.85 million

Some were total write offs.

Crash happened when the lead car, a Ferrari, hit a central barrier after losing control of the car while trying to overtake in wet conditions.

Perhaps in a testament to the cars' safety levels, none of drivers were seriously hurt.

The worst pileup in history happened on 11th December 1990 on Interstate 75 in Calhoun, Tennessee, USA, between Chattanooga and Knoxville near the Hiwassee River. A very heavy fog caused a 99-vehicle crash that killed 12.

Then there's the 17th March 2005 incident near Helsinki, Finland, that involved 300 cars, killing 3. It was caused by poor visibility due to heavy snowfall.