Do you want straight line performance or handling too? Import or domestic? Are you willing to work to make it fast/fun?

If you're looking for a fun ride: Miata
If you're looking for a fast ride: F-body or Fox Mustang
If you're looking for the total package: FC RX-7
If you're looking for the ultimate and don't mind working for it: Chevette with LS1 or Mazda Rotary and double-wishbone suspension

If you have more parameters it will be easier to give you more ideas.

-MR