Hm...the EG6 (Shingo's Civic SiR), the R32 (Nakazato's Skyline), and the AE86 Trueno (Takumi's car)...if it's Version 1, then the 86 is the way to go. If it's Version 2, then the EG6 is good for the wet, the R32 is...a decent training car, and the AE86 is fun, as well as an awesome training car. For Version 3, which I still have limited knowledge on, 86 for Akina, R32 for all wet courses, and EG6 for Happogahara (as far as I've been told).
Oh, and for those of you that actually wanna know...the top cars in each Version
Version 1:
FD3SI, followed by AE86
Version 2:
DC2, followed by FD3SI and FD3SVI
Version 3:
Dry: Cappuccino
Wet: Skyline R32
Akina Snow: Lancer Evo III