I'd say any of the M3's. In terms of tossability and road grip with a stock suspension, arguably the E30 318is or the M3. Could be completely true becuase of the light weight of those two, and that the E30's were still being built without much comfort in mind. I talked to someone on bf.c who owns an E30 318is and an E46 M3 (back when I was looking for an E30 and possibly considering a 318is), and he said the E30 is much more tossable, but in terms of trackability the E46 takes it hands down (probably becuase of power).
But the best answer will come from someone like big daddy or etc. who have probably driven a good number of different bmw's.