I'd have to agree with 2000V6SE, the 69-70 Boss 302 and Boss 429 are some of the fastest, best styled (IMO) cars made in that era... Plus anything with a 427CJ, or 428SCJ are just awesome...
The 71 Cuda, 69 Roadrunner, 69-70 Charger, 70 Challenger, 69-70 Mustangs, 69 Camaro, and a host of others from the muscle car era are some of the most sut-after cars... Get a Old car price guide and look at the values of some of these cars... Or watch a Barrett-Jackson Auto Auction some time and see what collectors are willing to pay for these cars...
As far as ugly cars go...
Yugo
Gremlin
Aztek
Lynx
****vette
and the list goes on