That I own? Ferrari 512M from 2000 that I got from some guy on Kijiji.
That I've found in stores? Probably the 2012 Hidden Super TH '67 Ford Mustang Coupe. For regulars, possibly either the '58 Impala or the Studebaker Avanti from the 2011 series.
That I don't have? Plenty... maybe the Ferrari F355 from the very first year of Treasure Hunts is my most-wanted of all time, but, more recently, I'm still annoyed that I didn't find a Datsun 240Z TH last year, and this year has the Ferrari 599XX Hidden super plus the '70 Camaro and the Ford Focus that I all want.
The Ferrari 355 was from 1996 and is a great example, but the first year of THs was 1995. There are so many to choose a favorite, but the 95 Cobra is up there and the 96 White Viper. How can you leave out the 95 '67 Camaro? I like the Lamborghini from 96, too.
Here's a rare one you don't see too often, the five spoke variation:
Recent nice ones are the 70 Camaro Super, Dairy Delivery, I like the Go Kart, yeah there's just too many!