Well, I have seen a lot of ugly cars over my lifetime. Some that really stand out are:
1. AMC Pacer.
2. Datsun B210
3. Most Peugots
4. Hummers, especially the H2.
5. Nissan Cube
6. Citroën 2CV
7. Pontiac Aztek
8. Lexus SC430
9. Chevrolet Avalanche
10. AMC Matador