For me, it was definitely the Ferrari Daytona *and* the AC Cobra battling in The Gumball Rally. I fell in love with the Ferrari after hearing it.
I watched Gumball on the TV in the late 70's in my early teens, and I was clearly impressionable. It was the first car movie I ever watched. When I got around to watching Smokey and the Bandit, I was baffled about why anyone who loved cars could even like that movie... sorry to all the Bandit fans, but that movie was about Bert and Sally, not cars. And that other garbage... Cannonball scum, sorry, same thing, except for the opening scene with the Countach, that was cool.
I am not a fan of remakes of TV shows or movies, but I think I would like to see a proper modern remake of Gumball - not that shite crap that the idiots are doing with the "3000" thing - they are hurting the Gumball name with their elitist idiotic behaviour (the make me think of Beavis & Butthead doing the Gumball, not car enthusiastic, and not even funny, just flat-out simply stupid).