When I initially bought the Z, it was going to be more of my fun car, while my DD was 2004 Civic Si. Now my civic sits in the garage while I drive my Z every day, Lol. I definitely understand where you are coming from in that you want a car that will be fun to drive so you'll take it instead of your Z.
I would go with a used SUV that you can find in manual like a 4runner or Jeep. I have bikes and other hobbies that need some good trunk space. If that's not your taste you can go with an e30/36 or subaru impreza rs.
Here's an article that might give you some ideas too:
Cheap Thrills: The 25 Best Low-Cost Hoonmobiles