Let's see...
1964 Pontiac Catalina
1977 Ford Van
1970 Mercury Grand Marquis, (429 c.i.d, burnt rubber for two blocks)
1968 Ford Mustang
1966 AMC Ambassador (ha ha, what a POS, but it was only $150, I couldn't resist.)
1984 Pontiac Fiero (first new car, not cheap, but also a POS)
1986 VW Jetta diesel
1988 Acura Legend Coupe
1991 Ford F150
1988 Ford Bronco
1986 Ford Taurus
1980 Yamaha Exciter 250
1963 Corvette Roadster
1958 Chevy Apache Pickup
1960 Ford F100 pickup
1998 Dodge Dakota
2001 Mazda Miata
2000 Dodge Intrepid
2003 Saturn L300 wagon
1993 Harley Davidson Fat Boy
1989 Harley Davidson FLHS Electra Glide Sport.
I am probably missing a couple here, but that's most of them.
So 21?
My favorite was the 1991 Ford F150, my least favorite was the Fiero, what a horrible, horrible car, especially since it was my first new car.
 
Edit, I forgot one, I may come up with more:
1993 Lincoln Mark VIII 
More as I remember them:
1985 VW Golf Diesel 
1993 Ford Explorer 
24, I win.