I've always thought the 2nd gen F-Body doesn't get enough credit for the design. This is one done right.
In general, I prefer newer car designs. There are a lot of older cars that I think look great, but the cars that really make me stop and stare are often newer ones.
I have to start with Aston Martin. No car maker is perfect, but Aston seems to hit more than miss.
As above, the DB5 is an older car that has great lines.
http://cdntbs.astonmartin.com/sitefinity/bond/bonddb53.jpg?sfvrsn=0
http://www.topgear.com/sites/default/files/styles/16x9_1280w/public/images/gallery-migration/2014-03/9FB67C61-288C-4D24-90C2-3EF962FB9E9C_2.jpg?itok=z5jQ4zTW
But as their designs progressed, I think they became better and better. Now there's the new Vanquish (love the name too):
http://3.bp.blogspot.com/-_HODVmaZmwU/VC2sR2nnKRI/AAAAAAAAJXc/fWTUz174voo/s1600/Aston-Martin-Vanquish-Carbon-Black-3.jpg
The lines are classic, but the trim is modern and aggressive. I love it.
Just don't let Zagato near it, or it all gets ruined.
I don't know what specifically catches my eye, but I know I love it when I want to wash the car so I have the excuse to run my hands over all the lines.