The Mystery Machine; (13 Ghosts of Scooby Doo Version) Yes, the original Mystery Machine is classic, but I loved the look of the updated red van, and wish it had been used beyond the intiial show.
The Biscuit Mobile: (Pound Puppies) Used in the episode 'Secret Agent Pup', it just seemed like such a fun vehicle, and once you the saw the actual scale of it compared to a human's size, it was beyond adorable.
The Turtle Van: (80's TMNT) The original party wagon. Who didn't want to drive this thing?
Ecto-1: (The Real Ghostbuster) Who knew driving a pimped out hearse could look so awesome?