- E21 323i
First BMW 300-series, the most powerfull of them. This litle sister, the 320i is a true legend from touring tracks.
- E30 M3 Evo3/Sport Evolution
No introduction needed, if you dont know what this is, you can shoot yourself(or atleast shame a bit).
- E36 M3 Evo (only sold in Europe)
2nd generation M3 whit 3.2 liter inline-6, producting 321hp @7400 and 350nm @3250.
- E28 M535i
If you dont count the M5, this is the most powerfull 2nd generation 500-series BMW with M-Technic aerodynamic kit, sport seats and unique 390 mm alloy wheels.
But because you wanted only one, my choose would be E21 323i, because its so rare in simulator games.