I have two Ford GTs and two E92 M3s. I leave one mostly stock and I max the other and make it a full-fledged track car. That's about it, I don't buy many cars more than once
Well, ignoring the X2010, the car I have the most of is the Alpine A110 1600S '73. Got that one three times. I actually think it's the only one I've got three times, but got many cars, including the Alpine A310 1600VE '73, twice.
I have 3 GTR Spec V 09's thanks to the first seasonal event. One is black with a carbon fiber hood, grouund effects and spoiler, One is red with a black spoiler. And I have one black that my son gifted me because he is thoughful back when you could trade more than one car per PS3.
RUFs... can't get enough of them, I always buy them when they show up in the UCD.
I usually have one stock, one mildly tuned, one balls to the wall, and one that replicates the Porsche on which that RUF was based. I wish the game had more RUFs...
I bought like 10 FIAT 500 (new version) and painted them like easter-eggs, yellow/red rims, blue/orange rims, turquoise/pink rims, green/yellow rims etc
I have maybe ten to twenty Ferrari F40s, just to sell if I need some quick cash at some point. After that I have six Formula GTs. I have three Ferrari F2007s and maybe a dozen or so other vehicles that I have two of, including (off the top of my head) the Ferrari F10 and Toyota 7.
I have five R35 GT-R's. A fully tuned SpecV, stock Spec V then two Academy Versions (one tuned, one stock) and a stock '07 model. Love that car. :-)
Also have four R34's of various tunes but one is the Mine's base model.
Currently, I have 26 X1's, 3x Vettel, 1x Prototype & 22 (20 0 Miles) coloured ones. Am recycling the UCD trying to collect all the veyrons, currently have 9, also have 11 FGT's.