Suggestions for a good summer car

+1.

Also, dunno how you feel about small cars but Toyota MR-S is a good fun car too. You can buy one already 2ZZ swapped for less than $15k and it should have Elise type power/weight and good handling.

NC Miata Club Spec package can be had for $11k these days, minimal weight and 170 hp, just add some wheels/tires/suspension and it will be a fun toy.

Of course NA/NB miata are the mainstays for cheap fun, see my PM if you are going this route.