What are the best Exotics you've spotted but can't seem to get a shot of or see a second time?

Mine are:
Bugatti Veyron Grand Sport
Miura SV
Diablo SE30
SLS BS

A couple of F430's in Cary. I would see one every few months (this was before I got into photography) and in the two years or so that I've been photographing cars, I haven't seen either once. Missed too many exotics in Charlotte to list.

Tons of stuff on the highway. Everything from Vantages all the way up to F430s and a Murcielago LP640.
I missed a red 458 spider a few years ago but luckilly I found it last Sunday :)
I miss this one Maybach in my town all the time. Its so annoying. Also, the same thing happens with a GT3 RS and a DB6.
I also missed the only Phantom DHC I've ever seen. White with tan interior.
When I was very young, 4 maybe, I attended a show with my dad in a nearby town that had an F40 and F50 present. Unfortunately, he didnt have a camera.

Venom GT
Phantom Drophead
Black Lexus LFA
LP 640 Roadster
4 458's
Countach and F355 combo
Bunch of ferraris bentleys lambos Astons and Maserstis
Rolls Royce Phantom Limo
Bentley Arnage limox3
SLS and Ghost combo
Jay Z's Maybach

Too much stuff to list. Some of the best include an LFA, SLR Mclaren (coupe and 722 Roadster), two Veyron Vitesses, Enzo, and F50.

- Ferrari 599 GTO

On the other side of the freeway:
. Either 3 599 GTO's or the same GTO 3 times
. A few Aventadors, two of them in one-off colors (one Verde Scandal and another some kind of red)
. Countach
. Several 458's and 599's

That's just naming a few; there have been tons.

Others:
. A white Aventador near my school. I got it at a red light, stood in front of it, turned my camera on, and got ready for a photo. My camera said my card was write-protected, so I took the card out, flipped the switch, and put it back in. Same message. I realized that the switch had come loose and would always switch to "locked" whenever I would put my card in. I didn't think to take the card out and just have the picture save to my camera, and I didn't have time to take out my phone, so I never got a photo. A few minutes later, an orange Murcielago came down the same road, and I could only get pictures with my phone. When I got home, I fixed it with a piece of scotch tape, and it hasn't given me any problems since. Also I did get photos of the same Aventador at a dealer.
. In Paris, I saw two SLS's, a 991 Carrera S, an R8, and a Phantom Drophead go by. I got ok photos of the R8 and the Phantom, and a very cr*ppy photo of one SLS.

ford gt
CGT x2
aventador
murcielago x2
ferrari 612
other random stuff

Huayra
Veyron Vitesse
regular Veyron
SLR x4
458 Special
Ford GT heritage edition
F40 x2
Yellow Enzo
Miura x2
Diablo x3
Aventador 50th Aniversario
And lots of other stuff including Aventadors, F12s, an LFA, Ford GTs, Murciélagos, Vanquishes, Mercedes Black Series and even more that I can't remember.

Ferrari F40
McLaren P1 in it's camo
Lamborghini's
TVR Tuscan 2 in pink
Maseratis
and so much more

I messed tons but the bigger ones have been:
Ford GT
Cali x2
Gallardo Spyder
Murcielago Roadster
360 x2
Diablo 6.0
Ferrari 550
Lotus Exige S
Phantom series II Sedan
Acura NSX
Ferrari F430
Ferrari Mondial T Cabrio
SRT Viper GTS x2
Maybach 57s

Most aren't really crazy exotics but from where I am these are the major misses

Ford GT
Rolls-Royce Wraith
Mclaren MP4-12C
Ferrari 458 x2
and others that I can't remember.

Enzo x2
Ford GT x2
Many 458s
F40
CGT
SLR x2
FFs
599 Alonso
DBS
SLSx3

Aventador and Ford GTX are two I saw but didn't shoot

la ferrari
pagani huayra
lamborghini lp640
10+ 458s
3x adventador
ferrari ff
ferrari f12