I sold mine raped it with the money glitch, Just I didn't want it anymore.. Its turning into a Futo now :\.
Yep I've noticed that the following have gotten incredibly popular (some are obvious, some are only starting to get popular):
Futo
Sultan
Adder
Entity XF
Vacca
Elegy RH8
Dominator
Z-Type
Stinger GT
Merryweather Mesa
Space Docker
Franklin's Buffalo
9F
Rat-Loader
Sheriff SUV
Coquette
Comet
And then there are some cars that are overlooked simply because of their looks. It's not how the car looks, but how it performs. Cars like this include:
Habanero (Why? Because it's a Lexus?)
Stratum (R32 Shooting Brake FTW. Also dangerously fast for Sedan class.)
Infernus (The Lampagani Zondalago at it's finest! Surprised not many have this car.)
Bison (It's a truck, albeit a kickass truck.)
Serrano (Hard to find, but well worth it. Easily the fastest SUV in the game.)
Surano (Not sure why this is ignored. It's fast as all heck for Sports class!)
Asea (A Dacia/Liana/Aveo combo that can be the ultimate sleeper. This thing is FAST when upgraded. Don't let its awful appearance fool you.)
Banshee (The almighty classic Banshee has been sidelined by the newer Coquette. Winning in this will prove that the Banshee still has what it takes.)
Ingot (Shameless ripoff of the Stagea that's...FWD. However when upgraded it can hold it's own in the Sedan class.)
Surge (Pretty fast for a Volt ripoff, and there's bodykits!)
Premier (Rare FWD Focus/Neon/Cobalt ripoff that is actually really fast when upgraded. Embarrass your opponents by trouncing them with a crappy entry level sedan!)