Ohhh, tough one.
I'd had to dig out my old printed photos, but it was probably my 1981 Pontiac Grand Prix LJ. Now have a weak spot for that generation of G-Bodies. It had replaced my 79 SJ which was destroyed by a FedEx truck making an illegal left turn. It was the beginning of having "freedom" as I was around 17-18 and started to venture out more. Plus, it was super clean, a 21k mile "old lady" car. Yeah, had the anemic 3.8 V-6, but it was my car, that I paid for with my own money.
I'd like to get another 92-96 Grand Prix GTP (with the 3.4), since I had a lot of adventures with it. Or even replace my 94 Honda Prelude SI 5spd (non-VTEC) with a 96 SI VTEC, since I had so much fun with it.
But that 81 GP is what started it all.