1. Traditional manual transmission (with a clutch you operate with your foot and a shifter you shift with your hand)
2. Rear wheel drive [puts on flame suit]
3. 2-door car (or 3-door, if you want to talk liftbacks/fastbacks/notchbacks/hatchbacks)
That's all. It can be a simple Nissan 240SX or the ultra exotic Mercedes Benz SLS. My friend stated that cars like the Mitsubishi Lancer Evolution should be added, but I argued that the Evo is a "performance vehicle", much like a Ford F-150 Lightning. He said I'm insane and made a video of my insanity.
So, what's your list of prerequisites for a "true" sports car? Here's some of my favorites: