By abnormal, I mean, not in the usual SUV (for Baja), coupe, hatchback or sedan forms. I'd allow exotics if you don't normally see them in a rally guise (i.e. Top Gear Bentley Conti GT).
Personally, I'd like to rally a Toyota Previa 4WD (rally prepped of course! unless I want to do barrel rolls). FMR Layout. Four wheels on the ground. 5-speed manual. 8 Seats. The title of the ultimate minivan hoon machine.
Oh and it's pretty damn cheap
Here's some other less usual ones
Mitsubishi Delica Rally Van
the way kinja formats stuff is making me cry :(