My favorite F1 cars:
In the category "Great looking flaws, designed by people who knew little of engineering":
The Eiffelland-March 721(1972)
In the category "Utterly beautiful, decently competitive":
The Arrows A2 (1979)
In the category "Only have a N/A Ford V8 to race against those powerful turbo machines, let's fight drag":
My personal all-times favorite Benetton B189 (1989)
And in the category "Engineering masterpieces":
The Lotus 78 (1977)
The Lotus 88 (1981)
Edit: I seem to have a difficult time counting 'till 5...
I've edited because I put 6 cars the first time.