I suppose by definition "rare" means "fewest produced." So to answer your original question, I'd start by pointing out there were many
one-off Cobras:
- CSX2000 - original Cobra prototype and the only one with inboard rear brakes
- CSX2008 - Cougar II styling concept
- CSX2131 - Willment Cobra Coupe
- CSX2196 - "flip top" roadster
- CSX2451 - Mercer-Cobra
- A-98 - AC Le Mans Coupe
- CSX3001 - XD Cobra styling concept
- CSB3054 - Type 65 Daytona 427 Super Coupe
- CSX3055 - Willment/Ghia 427 Coupe
- CSX3198 - 427 Dragon Snake
In addition there were several
low-production runs of special Cobras:
- 427 Twin-Paxton "Super Snakes" (2 produced)
- 289 Slalom Snakes (2 produced)
- 289 Sebring roadsters, factory team cars (3 produced)
- 260/289 Dragon Snakes, factory team cars (2 produced)
- 289 Dragon Snakes, factory-prepared customer cars (4 produced)
- 289 FIA roadsters, factory team cars (5 produced)
- 289 USRRC roadsters, factory team cars (6 produced)
- 289 USRRC roadsters, factory-prepared customer cars (5 produced)
- Cobra Daytona Coupes (6 produced)
- 289 Le Mans hardtop coupes (7 produced)
Have I missed any...?