"A rat rod is a style of hot rod or custom car that, in most cases, imitates (or exaggerates) the early hot rods of the 40s, 50s, and 60s. It is not to be confused with the somewhat closely related "traditional" hot rod, which is an accurate re-creation or period-correct restoration of a hot rod from the same era.
Most rat rods appear "unfinished" (whether they actually are or not), with just the bare essentials to be driven.
The rat rod is the visualization of the idea of function over form. Rat rods are meant to be driven, not shown off. Sometimes the customization will include using spare parts, or parts from another car altogether."
Here is a collection of photos for your enjoyment! As for my favorite: it's a toss up between the VW Bug and the Tudor Sedan (though the drag car with the shifter outside the driver's window is real sweet!).