tis a tricky question. I agree with Gok that the 'normal' cars of the early G1 line were what made the idea of Transformers so interesting.

But I don't think that's the point of this thread, this thread is of all the cool 'realistic', civilian alt modes through the history of the franchise.

I would get a kick out of driving around a 'G1 Skids' my first toy, along with Thudercracker.
I would also get a kick out of driving around an 'Alternators Wheeljack', or a movie soundwave.

If I had stupid amounts of Money though I probably wouldn't even go to the trouble of a 'G1 Prime', it'd have to be 'Movie Ransack'. I'd have the money and make the time to get me a civil pilots license and any old WW1 Biplane is going to stand out, but in a 'cool collectable' kind of way.

I would drive to the airstrip in a Movie Lockdown.