mondo84: Is Stunts too old to put forth? I'd say Stunts. I loved the track editor in that game.
Stunts was awesome. Beware the mad skills of Skid Vicious! As I kid a friend of mine and I spent countless hours designing tracks. It was one of those ahead-of-its-time sims, like
Forgotten Realms Unlimited Adventures, that had a dedicated community for years to come.
Need For Speed: High Stakes (1999) was probably my favorite. The game allowed you to install it to the hard drive and play it without the game CD...and substitute a music CD in the "car stereo" which would play instead. I remember always playing Soundgarden, Screaming Trees, and Pearl Jam CDs in the CD-ROM drive whilst playing it and now
Yield is always (fittingly) associated with this game.