I wouldn't say there's much rare tbh, more hard to obtain...
In my garage currently, I'd say the more obscure vehicles would be:
Declasse Tornado hardtop
Vapid Bobcat XL hard top rear
I've had a Phoenix on a couple of occassions but prefer the Ruiner for some reason.
Only other thing I'd fancy getting my hands on is the Tailgater... but I'm going to have to do a bit of a garage swap around with my 2nd character to get an Asea for my main (stickerbombs ahoy! ) and get a classics garage for the 2nd character and keep her for driving and nothing else..