USA (home)
Canada
Bulgaria
England
Scotland
Ireland
Wales
Australia
Costa Rica
Croatia
Slovenia
France
Hungary
Jersey
Kazakhstan (driven, not rented)
Russia (driven, not rented)
Namibia
Oman
Panama
South Africa
Spain
UAE
Yemen (driven, not rented)
By far the hairiest driving was in Costa Rica, due to the fact that I was driving through torrential rain in a tropical storm, at night, on a highway with potholes so big you could have fit a rowboat into them. Worst traffic: Moscow. Most pleasantly surprising: Namibia.