"Cultures of Corruption: Evidence From Diplomatic Parking Tickets," is a paper by Columbia's Ray Fisman and UC Berkeley's Edward Miguel that investigates the number of unpaid diplomatic parking tickets by country to formulate an index of each country's corruption. Diplomats don't pay parking fines, so the only reason for diplomats to follow the law is conscience and respect for the rule of law.
The worst offenders are the Kuwaitis, whose nine diplomats have racked up 246.2 violations each; then Egypt, with 139.6 violations for 24 diplomats. Canada, Israel, Norway, Sweden, and Denmark have no violations at all.
Update: Joe sez, "The US embassy in London owes UKP 271,000 (just over half a million dollars, give or take) in fines for their ongoing refusal to pay the London congestion charge. The diplomats claim it's a tax, the London authorities say it's a charge for a service."
Update 2: Keith sez, "The £271,000 owed by US diplomats is just from the last 6 months. The sum since the scheme began in 2003 is many times more: "The US Embassy in London now owes £891,000 (that is $1.6 million)."