That's an easy one: Microprose Formula 1 Grand Prix. Played it until 2000ish on a frequent base :-). I know there were others even more adicted to it (like the authors of F1GPed) but I even went through the pain of writing an AmigaBASIC program that would help setting-up the gearbox. It enabled me to become world-champion in Pro mode, in a Minardi ;-).
Even re-wrote it in ACE-BASIC so that I didn't have to turn off the FastMem (NoFastMem) for running the tool on the old A3000.
